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literature review and methods

Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.



How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

Systematic Reviews

What Makes a Systematic Review Different from Other Types of Reviews?

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91–108. doi:10.1111/j.1471-1842.2009.00848.x

Methods and the Literature Review

by Janet Salmons, PhD, Research Community Manager for SAGE Methodspace. Research design is the focus for the first quarter of 2023.

How do you know where you going if you don't know where you've been?

literature review and methods

Reviewing literature to situate it in a research tradition is an essential step in the process of planning and designing research. A literature review shows the reader where your research is coming from, and how it is situated in relation to prior scholarship. Attention is necessarily given to literature about the research problem, which places the study in one or more disciplines. To situate the study within a scholarly milieu, we must also review literature about methodology and methods.

In other words, the literature review should include not only what has been studied, but how it was studied. Has this problem been largely investigated using quantitative methods? If so, how might a qualitative study contribute to the field? Has the problem generally been studied from individual perspectives, using interviews to collect data? If so, how might the problem be studied from a group, organizational, or societal perspective? Or how might it be studied using Big Data and computational methods? If you are studying a problem in a sociological discipline, might it be useful to look at how the problem has been researched in other disciplines, such as education or public policy? By exploring these kinds of questions you can find new perspectives on how to study your selected problem, and substantiate the approach you decide to take.

What is a literature review ?

Literature reviews are foundational to research proposals, theses and dissertations, as well as scholarly books and articles. In addition to their place within larger pieces of writing, literature reviews are also published as a type of free-standing article. (See Designing Review Research .)

Let's use a simple definition for a literature review: "a systematic syntheses of previous work around a particular topic" (Salkind, 2010, p. 726) . The key words suggest questions we need to answer:

What systems will we use to find, organize, and analyze the literature?

How will we synthesize the literature?

Which previous work should be included or excluded?

What topics are relevant?

Specific to a review of methodology and methods literature, we might ask:

What systems will we use to find, organize, and analyze literature about the methodology and methods central to the study? How can we find the respected methodologists and theorists whose work is most relevant to our research? Does it make sense to organize this literature chronologically, or thematically?

Which previous work should be included or excluded? Whose thinking should inform the approaches we use in our own research? What disciplines should be included, beyond our own field of study? Who are the respected methodologists and theorists in this type of research? Do these thinkers agree or disagree, if so, why? Are there multiple schools of thought that we should consider? How do we define "previous" in terms of time frame, how far should we go back? How do we think about previous work when we are using emerging methods?

How will we synthesize the literature? What critical questions should we ask? How can we pull essential concepts, theoretical constructs, and methods practices from different sources to substantiate design decisions regarding the research approach?

What topics are relevant? How do I find methodological and methods literature that relates to the proposed study?

What types of sources should inform the methodological and methods section of a literature review?

While literature reviews typically draw on articles from peer-reviewed journals, the methodological and methods section of a review may also contain books. The lengthy, in-depth descriptions of methodologies and methods are more often presented in book form. When reading journal articles about your topic of study, check the reference list for sources about the methods used.

System or chaos?

literature review and methods

The first key word in Salkind's definition is system. Let's start by exploring systems we can establish to organize, and analyze literature about the methodology and methods central to the study. Without a workable system, the other tasks associated with the literature review can become more difficult to achieve. I've experienced this dilemma: “I know I've read just the right resource, but where is it in the midst of piles and files of documents?” Here are some open access chapters and companion sites for a few relevant SAGE books about literature reviews. If you want to purchase one of them, use the code MSPACEQ123 for a 20% discount, valid until March 31, 2023.

Systematic approaches to a successful literature review (Booth, Sutton, & Papaioannou, 2016). Available resources include a Companion site and Chapter 2 . This book includes steps for students and experienced scholars, with discussion of a variety of literature review types.

Conducting research literature reviews:From the Internet to Paper (Fink, 2019). Available resources include Chapters 1 and 2 . This edition includes recommendations for organizing literature reviews using online resources. Chapter 2 discusses how to look for methodological quality in the sources you select. 

Doing Your Literature Review: Traditional and Systematic Technique s (Jesson, Matheson, & Lacey, 2011). Chapter 1 is available to download. It offers foundational definitions and exercises you can try.

Salkind, N. J. (2010). Literature review. Encyclopedia of Research Design. Thousand Oaks, California.

More Methodspace posts about the literature review

Review Research: An Interview with Dr. David Denyer

How can you use published literature as data? In this Methodspace interview Dr. David Denyer explains how and why to use review research.

Methods and the Literature Review

A critical step in planning and designing research entails reviewing literature to situate it in a research tradition.

Synthesizing Methods Literature

Find tips for organizing and synthesizing sources for your literature review.

Literature Reviews and Review Research

Want to design and plan a review study? Find open-access examples of systematic reviews, meta-syntheses, meta–analyses, and integrative literature reviews. Also, learn more with related SAGE books.

Designing Literature Reviews as a Research Project

Review research has become a credible and legitimate form of scientific inquiry in various fields of science including management and organizational sciences. Find open-access articles with practical advice about planning a review study.

How to Write, Evaluate, and Use Methodological Literature Reviews

Dr. Helen Kara offers suggestions for taking an ethical approach to your literature review.

Methods Literature as Part of a Review

Designing qualitative research with the Total Quality Framework

Synthesizing methods literature.

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Introduction, section snippets, references (405), recommended articles (6).


Computers & Industrial Engineering

Application of madm methods in industry 4.0: a literature review.

Industry 4.0 has received inordinate attention from the business as well as research communities. Along with the development of Industry 4.0 applications and the diversity of potential alternatives, Multi-Attribute Decision Making (MADM) techniques have been employed by researchers as systematic approaches to support the decision-making processes. However, as the adoption of Industry 4.0 technologies requires considerable capital, and as it is relatively difficult to identify the suitable MADM method for the decision-making process in certain conditions, it becomes necessary to determine which components of Industry 4.0 are most commonly in demand of MADM applications of decision making, and which MADM techniques are mostly preferred by researchers and businesses for varied directions of Industry 4.0. Therefore, this study aims to provide a comprehensive review of MADM methods and their applications for different components of Industry 4.0. A methodology, including a review framework, is provided for the related analyses. The proposed framework includes analyses concerning methods, subtopics, and bibliometry along with the related exploratory tables and figures. Finally, the trends and research gaps are clearly stated to shed light on the further research areas taking into consideration different challenges that can be encountered by researchers, along with a set of propositions to potentially overcome them.

As a result of industrialization and globalization, technological developments have led to paradigm shifts widely known as industrial revolutions (Lasi et al., 2014). Industry 4.0 is a term that was initially introduced in 2011 at the Hannover Fair and the concept has spread in various fields year by year (Vogel-Heuser and Hess, 2016). After the introduction section, the term has been used mostly in high-tech projects by the German state (Steiner, 2019). Industry 4.0 presents a technique for developing a transition from machine-dominant production to digital production (Oztemel & Gursev, 2020). The 4.0 label implies that this is the fourth industrial revolution in the world, the heir to three previous industrial revolutions that created massive changes in productivity and improved people's lives all around the world (Davies, 2015). The key principle of industry 4.0 is the development of “smart factories,” which is mainly related to the cyber-physical systems (CPS) of the manufacturing plants (Steiner, 2019). A smart factory is described as the use of advanced digital technology innovations including “advanced robotics and artificial intelligence; sophisticated sensors; cloud computing; the Internet of Things (IoT); data capture and analytics; digital fabrication (including 3D printing); software-as-a-service and other new marketing models; smartphones and other mobile devices; platforms that use algorithms to direct motor vehicles (including navigation tools, ride-sharing apps, delivery and ride services, and autonomous vehicles); and the embedding of all these elements in an interoperable global value chain, shared by many companies from many countries” and these elements may be a connection between machine and human (Geissbauer et al., 2016).

The rapid evolvement of Industry 4.0 technologies resulted in more alternatives for businesses. The decision-making process for different components of Industry 4.0 is a non-trivial problem and requires complex control subsystems. As most of the real-life problems having various and frequently conflicting criteria, objectives, and goals, Multi-Criteria Decision Making (MCDM) methods play an important role in dealing with these problems in a systematic approach. There are two main parts of MCDM. These are Multi Attribute Decision Making (MADM) and Multi Objective Decision Making (MODM) methods. The main difference between them is the number of alternatives. There is a countable number of alternatives within MADM methods. On the other hand, the number of alternatives is infinite in MODM methods. There are more than fifty methods under MADM (Watrobski et al., 2019) but not every method can be used for solving every decision-making problem. MADM models are used in different roles in the concept of Industry 4.0. For instance, the AHP method, which is one of the remarkable MCDM models, has been used by various researchers in the cloud computing environment. Patiniotakis et al., 2013, Kumar and Kumar, 2016 presented assessment systems for cloud service providers by employing fuzzy AHP. Ramachandran et al. (2014) utilized the AHP method to select a suitable cloud computing technology deployment model for an academic institution. Moreover, using Fuzzy TOPSIS, Sohaib and Naderpour (2017) evaluated the technological, organizational, and environmental factors of public cloud computing service models in the context of e-commerce. In the article of Yadav and Goraya (2018), AHP was used to rank both cloud service providers and service requesting customers. Saidi et al. (2019) proposed a deep supervised learning-MCDM model using the ELECTRE III and ELECTRE TRI approaches for energy consumption awareness in cloud computing. For the selection of production simulation software in the Industry 4.0 environment, Cafasso et al. (2020) employed an MCDM approach called Best Worst Method (BWM). To effectually evaluate alternative technologies that combine microelectromechanical systems with integrated circuits, Lee et al. (2021) proposed an integrated approach using Fuzzy AHP and Fuzzy VIKOR. Finally, in the paper of Sadreddini et al. (2021), a smart reservation system is proposed that considers the behavior of electric vehicle (EV) utilizers, the availability of parking spaces, and the state of EV charge. They used AHP in their smart reservation system to consider weighting the behavior of EV users.

Since the implementation of Industry 4.0 technologies requires considerable capital, businesses have to select the best-fitting technologies amongst the available alternatives. This process can be risky and requires an appropriate evaluation of all the options considering all the criteria (Soni et al., 2022). Although there are many MCDM methods, the characteristics of each method can be very different. Each method has its advantages and disadvantages, and different results can be obtained by applying different methods (Zardari et al., 2014). Therefore, selecting the appropriate method for the decision-making process can be very difficult (Bajec & Tuljak-Suban, 2019). Applying decision-making methods for Industry 4.0 technologies makes the problem even more challenging (Bai et al., 2020). First, there is a general lack of knowledge regarding the real benefit of Industry 4.0 technologies because they are relatively new. Second, the integration of these technologies with the traditional production system adds more restrictions to the application of Industry 4.0 technologies. Third, the performance of these technologies is associated with uncertainties due to the different contexts of applications and the diversity of industries. Finally, Applying an unsuitable method can lead to inaccurate decisions which might result in spending a lot of money on unfitting technology.

So far, the literature has been quiet on addressing these challenges, which made it a necessity to shed more light on the areas of Industry 4.0 where decision-making methods are most needed and to identify which MADM methods are mostly implemented for each direction of Industry 4.0. Using the most-fitting MADM method can aid organizations in further understanding and adopting Industry 4.0 technologies. Hence, a systematic literature review methodology is applied to guide the researchers as well as business practitioners to make the right decision and reach the best outcome of applying MADM methods in the scope of Industry 4.0 which is the main purpose of this literature review.

Due to the popularity of Industry 4.0 and MADM techniques, various literature review studies have been provided by the literature for both topics. Earlier review studies about the application of MCDM methods include supplier evaluation and selection (Ho et al., 2010, Chai and Ngai, 2020), green supplier selection (Govindan et al., 2015), and corporate sustainability (Chowdhury & Paul, 2020). On the other hand, some of the literature review studies about Industry 4.0 include the past, present, and future of industry 4.0 (Liao et al., 2018), the related technologies (Alcácer & Cruz-Machado, 2019; Oztemel & Gursev, 2020), industry 4.0 and lean manufacturing (Pagliosa et al., 2019) and the smart factory as a key construct of industry 4.0 (Osterrieder et al., 2020). To the best of our knowledge, there is not a literature review study about the application of MADM methods in Industry 4.0, hence this study is the first attempt to reveal the research gaps and future trends regarding the applications of MADM methods in Industry 4.0. In addition, this study is important with respect to classifying MCDM methods employed in the domain of Industry 4.0 and being one of the first papers in this area to include subject, method, and bibliometric analysis with the clarification of trends and research gaps.

This research shows the trend of interest in MADM applications within the scope of Industry 4.0 over the years.

This research provides information about which MADM methods are most used by researchers for Industry 4.0 components and compares the results obtained in different components.

This research specifically shows where MADM applications are most needed within Industry 4.0.

This research highlights the appropriate MADM methods for each Industry 4.0 component and demonstrates the link between a particular component and a particular method.

This research addresses the challenges researchers face and offers recommendations for managing them.

The remainder of the study is organized as follows. Section 2 provides the research methodology utilized during the review process. Theoretical background about MADM methods is provided in Section 3. Section 4 includes the components of Industry 4.0. The review results including MADM methods are presented in Section 5. Section 6 includes the trends and research gaps including the challenges and the propositions to overcome them, and finally, the conclusion is provided in Section 7.

Research methodology

The structure of this systematic literature review is constructed based on the works of Lange and Pfarrer, 2017, Denyer and Tranfield, 2009. The methodology of Denyer & Tranfield (2009) has been implemented in many other literature reviews in the fields of supply chain management and big data analytics (Espadinha-Cruz et al., 2021, Ghadge et al., 2012, Tachizawa and Yew Wong, 2014, Shayaa et al., 2018, Tukamuhabwa et al., 2015) whereas similar methodologies are used in the studies of

Brief theoretical background about MADM methods

The MADM methods are divided into six groups including pairwise comparison, distance-based, outranking, interaction-based, utility-based, and other methods as illustrated in Fig. 3 (Yalcin et al., 2022). Each group consists of various subgroups and methods.

The main characteristic of MADM methods is that there is a limited number of alternatives in the decision-making problem. An interaction-based method class is added to the classification provided in the study of Kahraman et al. (2015). Brief

Components of Industry 4.0

Industry 4.0 has attracted much attention in recent literature. The adoption of Industry 4.0 technologies has been identified as a major contributor in the context of digital and automated manufacturing environments (Kamble et al., 2018). However, there is no agreed list of Industry 4.0 enabling technologies in the literature; scholars lack mutual understanding and there are some inconsistencies among the different literature domains (Fettermann et al., 2018, Riel and Flatscher, 2017). In this

Review results

As stated before, the literature review is performed based on three main analyses. These are the method, topic, and bibliometric analysis. These analyses will be performed for the studies including MADM methods.

Trends and research gaps

By analyzing the trend topics, Fig. 19 shows an increasing interest in Industry 4.0 in general and in IoT, big data, and cloud computing in particular. Although the number of papers or keywords that targeted cloud computing was much more than IoT and big data, analyzing the data showed more recent interest in these two topics with MADM methods. As for the MADM methods, AHP and TOPSIS are still favorable by most researchers due to the effectiveness and popularity of these two methods.

The purpose

Summary and conclusion

The Industry 4.0 concept was first presented by the German government to encourage computerization in manufacturing. The proposed concept has received a lot of attention and become widespread due to the benefits provided by companies as a result of Industry 4.0 technologies. Hereby, businesses started to invest in Industry 4.0 technologies (Ozdemir, 2022). However, since the implementation of industry 4.0 technologies requires a significant amount of capital, firms have to choose the most

CRediT authorship contribution statement

Wael Zayat: Conceptualization, Formal analysis, Investigation, Writing – original draft. Huseyin Selcuk Kilic: Methodology, Writing – original draft. Ahmet Selcuk Yalcin: Conceptualization, Writing – original draft. Selim Zaim: Supervision, Conceptualization, Methodology, Writing – review & editing. Dursun Delen: Conceptualization, Methodology, Validation, Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Trading performance evaluation for traditional power generation group based on an integrated matter-element extension cloud model

Energy reports, selection of industrial robots using compromise ranking and outranking methods, robotics and computer-integrated manufacturing, decision-making techniques in supplier selection: recent accomplishments and what lies ahead, expert systems with applications, improved decisions for marketing, supply and purchasing: mining big data through an integration of sentiment analysis and intuitionistic fuzzy multi criteria assessment, computers and industrial engineering, a novel pythagorean fuzzy set integrated choquet integral approach for vertical farming technology assessment, promethee: a comprehensive literature review on methodologies and applications, european journal of operational research, industry 4.0 technologies assessment: a sustainability perspective, international journal of production economics, a hybrid multi criteria decision method for cloud service selection from smart data, future generation computer systems, scanning the industry 4.0: a literature review on technologies for manufacturing systems, engineering science and technology, an international journal, network selection criterion for ubiquitous communication provisioning in smart cities for smart energy system, journal of network and computer applications, zbwm: the z-number extension of best worst method and its application for supplier development, nmcda: a framework for evaluating cloud computing services, internet of things (iot) and its impact on supply chain: a framework for building smart, secure and efficient systems, a bipolar neutrosophic multi criteria decision making framework for professional selection, applied sciences (switzerland), utilising neutrosophic theory to solve transition difficulties of iot-based enterprises, enterprise information systems, technology analysis for logistics 4.0 applications: criteria affecting uav performances, studies in systems, decision and control.

DM-MCDA: A web-based platform for data mining and multiple criteria decision analysis: A case study on road accident

Complex spherical fuzzy sets and an application to catering services in aviation 4.0.

The challenges of instructors’ and students’ attitudes in digital transformation: A case study of Saudi Universities

Education and information technologies, fuzzy multicriteria decision-making approach for measuring the possibility of cloud adoption for software testing, scientific programming, mobility-aware container migration in cloudlet-enabled iot systems using integrated muticriteria decision making, international journal of advanced computer science and applications.

Ranking cloud render farm services for a multi criteria recommender system

Sadhana - academy proceedings in engineering sciences, decision making in cloud environments: an approach based on multiple-criteria decision analysis and stochastic models, journal of cloud computing, sentiment analysis technique and neutrosophic set theory for mining and ranking big data from online reviews, ieee access, technology selection for iot-based smart transportation systems, advances in intelligent systems and computing.

Process Mining Approach of a New Water Quality Index for Long-Term Assessment under Uncertainty Using Consensus-Based Fuzzy Decision Support System

Water resources management, what’s new in icu in 2050: big data and machine learning, intensive care medicine.

Load-Balancing Algorithm for Multiple Gateways in Fog-Based Internet of Things

Ieee internet of things journal, moving towards smart cities: a selection of middleware for fog-to-cloud services.

Participant trustworthiness analysis in the game-based urban planning processes by PROMETHEE-mGqNN approach

Infinite study.

Building supply-chain resilience: An artificial intelligence-based technique and decision-making framework

International journal of production research, a novel multiclass priority algorithm for task scheduling in cloud computing, journal of supercomputing, implementing a cloud-based decision support system in a private cloud: the infrastructure and the deployment process, international journal of decision support system technology, a network qos aware service ranking using hybrid ahp-promethee method in multi-cloud domain, international journal of engineering research in africa, a practical approach to cluster validation in the energy sector, energy informatics.

Cited by (0)

Consensus improvement model in group decision making with hesitant fuzzy linguistic term sets or hesitant fuzzy linguistic preference relations.

Hesitant fuzzy linguistic term sets (HFLTSs) and hesitant fuzzy linguistic preference relations (HFLPRs) are widely used where decision makers are permitted to provide qualitative preferences with several linguistic terms over two alternatives. There are several issues deserving further investigation in the existing consensus models of HFLTSs and HFLPRs: the extension process of HFLTSs which is always performed in distance measure and aggregation of HFLTSs distorts the original information, the modified HFLTSs does not belong to standardized HFLTSs, and most of the existing models don’t discussed the number of optimal solutions. In order to solve the above problems, this paper introduces new distance and entropy measures for HFLTSs, by which information aggregation method and two consensus improvement models in group decision making (GDM) with HFLTSs and HFLPRs are proposed. The first model is a four-stage optimization model with four objectives, based on which an equivalent linear weighted optimization model is derived by assigning appropriate weights to four objectives with different priorities. According to either of these two models, the revised individual and collective opinions can be obtained. In addition, the prominent properties of the collective opinion obtained from optimization models are further investigated. As last, some examples are provided to demonstrate the applicability of the optimization models proposed, and the results demonstrate the models proposed can better deal with the abovementioned issues.

Decision field theory-combined multi-attribute group decision-making method for incomplete linear ordinal ranking

In practice, experts sometimes compare alternatives from different perspectives by rankings to express their preferences. However, it is common that the comparing information they give is incomplete, and experts’ preferences are changing during the decision-making process. In this situation, it is not easy to depict experts’ preferences and making appropriate decisions. Hence, to handle the problems, this paper proposes a multi-attribute group decision-making (MAGDM) method for incomplete linear ordinal ranking (ILOR) information combined with the decision field theory (DFT) from the perspective of process-oriented decision-making. Firstly, the extended preference map and information energy for ILOR are improved. Based on those, the concept of probabilistic utility set (PUS) and some basic operations are proposed to enhance the computability of ILOR, which can convert incomplete ILORs to PUS and depict the experts’ preferences effectively. Then, the framework and the detailed steps of the DFT-combined MAGDM method are presented, in which the psychological difference for PUS is established. The method helps depict the distance felt by experts and the variability of the decision-making process. Finally, the illustrations are conducted to show the usage and features of the proposed method. The illustration shows the good interpretability and accuracy of the method.

Impact of government subsidy on diagnostic tests decisions of core products in high-end equipment manufacturing

In the high-end equipment manufacturing industry, diagnostic test is a common procedure for core products. The core component supplier could obtain the true quality of its products by implementing diagnostic test during the R&D (research and development) process and adjusting the efforts to achieve better quality. However, diagnostic test is not well implemented due to its high cost. As China’s favorable policies increase in relevant regard, government subsidy becomes an emerging incentive for core product manufacturing. The core product supplier who receive financial incentives usually contributes extra effort to achieve better quality. However, the extra effort comes with a corresponding cost. In addition to this, the supplier has received government subsidy to fund the implementation of diagnostic test. In turn, conducting diagnostic test can provide a safety plug as to whether the supplier should receive government subsidy. To investigate this interaction between the government subsidy adoption decision and the diagnostic test decision, we use game theory to model a supply chain composed of an upstream supplier and a downstream manufacturer, where the supplier is delegated by the manufacturer to research and development a batch of core products and to maintain them during the warranty period. Our research shows that even though government subsidies can provide the supplier with direct financial support, it may still not be adopted. In essence, government subsidy has a bright side and a downside effect on supplier, wherein the former side is the direct financial support and the downside is the extra effort cost. The supplier does not always accept government subsidy because the bright side not always sufficient to cover the downside. Specifically, when diagnostic test is costly or with high-quality products, the supplier will accept subsidy but not perform diagnostic tests regardless of government subsidy. Counterintuitively, if consumer preferences for the product are high, the supplier will choose not to accept government subsidy but to perform diagnostic test. This research contributes to providing some theoretical insights for managers in the high-end equipment manufacturing industry.

A new hierarchical multiple criteria ordered clustering approach as a complementary tool for sorting and ranking problems

Multiple criteria ordered clustering is a problem that involves grouping the objects of decisions (actions) into a priori unknown ordered classes considering the preferences of a decision maker (DM). By exploring the relationship between multiple criteria sorting and multiple criteria ordered clustering, we take advantage of some ordinal classification approaches to propose a new approach. The set of totally ordered clusters fulfills a property of monotonicity with respect to dominance and an asymmetric preference relation; this is useful for suggesting a more consistent and robust rank of actions regarding the existence of possible “irrelevant alternatives”. The algorithm designed to operationalize our approach makes use of either a fuzzy outranking relation or a fuzzy preference relation. Imperfect knowledge (namely uncertainty and imprecision) of criteria performance levels and model parameter values can be modelled using interval numbers. Our approach and algorithm are illustrated through a simple interval extension of the well-known PROMETHEE method, which is applied to group countries according to human development criteria. The OECD country governments are also grouped according to their public sector performance but instead using a fuzzy outranking relation in an interval framework. In both examples, the results are very promising.

Consensus driven preference analysis model for incomplete group decision making with the multiple criteria hierarchy process

Most real-life group decision making issues involve incomplete assessments under hierarchical criteria due to limited knowledge and experience of decision makers, which entail diverse challenges including information filling, consensus reaching and preference fusion. To cope with them, an incomplete information-filling method is first presented based on the objective data and subjective willing. Then to improve the flexibility and compatibility, a novel group consensus measurement is defined based on the norm theory, which considers the influence of label preference ignored by the distance-based consensus measurements. Finally, differently from the existing group decision making methods that infer a consensus result through aggregating all individual preferences, this study develops a consensus driven preference analysis framework to derive the preference relationships among alternatives and further obtain the final ranking result using the representative value function. An application example of a sustainable supplier selection is carried out to illustrate the proposed methodology, and sensitivity and comparative analyses are performed to exhibit its flexibility and effectiveness.

Integrated parameter and tolerance design for multiple response optimization

Robust parameter design and tolerance design are effective approaches for continuous product quality improvement. However, the traditional two-stage design approach of parameter design followed by tolerance design is time-consuming. The tolerance levels determined in the tolerance design stage typically affect quality loss; therefore, the parameter levels obtained in the parameter design may be suboptimal. In this paper, we propose an integrated parameter and tolerance design model, and then a criteria importance through intercriteria correlation-based grey relational analysis technique is adopted to obtain the optimal parameter and tolerance levels. A case study is conducted to validate the proposed method. Comparison results show that the parameter levels and tolerance levels of controllable factors obtained using the proposed method are more reliable and enable a better tradeoff among quality loss, tolerance cost and predicted loss.

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Research Methods and Design

Literature Review

A literature review is a discussion of the literature (aka. the "research" or "scholarship") surrounding a certain topic. A good literature review doesn't simply summarize the existing material, but provides thoughtful synthesis and analysis. The purpose of a literature review is to orient your own work within an existing body of knowledge. A literature review may be written as a standalone piece or be included in a larger body of work.

You can read more about literature reviews, what they entail, and how to write one, using the resources below. 

SAGE Research Methods Videos

Am i the only one struggling to write a literature review.

Dr. Zina O'Leary explains the misconceptions and struggles students often have with writing a literature review. She also provides step-by-step guidance on writing a persuasive literature review.

An Introduction to Literature Reviews

Dr. Eric Jensen, Professor of Sociology at the University of Warwick, and Dr. Charles Laurie, Director of Research at Verisk Maplecroft, explain how to write a literature review, and why researchers need to do so. Literature reviews can be stand-alone research or part of a larger project. They communicate the state of academic knowledge on a given topic, specifically detailing what is still unknown.

This is the first video in a whole series about literature reviews. You can find the rest of the series in our SAGE database, Research Methods:

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Organizational Tools for Literature Reviews

One of the most daunting aspects of writing a literature review is organizing your research. There are a variety of strategies that you can use to help you in this task. We've highlighted just a few ways writers keep track of all that information! You can use a combination of these tools or come up with your own organizational process. The key is choosing something that works with your own learning style.

Citation Managers

Citation managers are great tools, in general, for organizing research, but can be especially helpful when writing a literature review. You can keep all of your research in one place, take notes, and organize your materials into different folders or categories. Read more about citations managers here:

Concept Mapping

Some writers use concept mapping (sometimes called flow or bubble charts or "mind maps") to help them visualize the ways in which the research they found connects.

literature review and methods

There is no right or wrong way to make a concept map. There are a variety of online tools that can help you create a concept map or you can simply put pen to paper. To read more about concept mapping, take a look at the following help guides:

Synthesis Matrix

A synthesis matrix is is a chart you can use to help you organize your research into thematic categories. By organizing your research into a matrix, like the examples below, can help you visualize the ways in which your sources connect. 

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Research Methods: Literature Reviews

A literature review involves researching, reading, analyzing, evaluating, and summarizing scholarly literature (typically journals and articles) about a specific topic. The results of a literature review may be an entire report or article OR may be part of a article, thesis, dissertation, or grant proposal. A literature review helps the author learn about the history and nature of their topic, and identify research gaps and problems.

Steps & Elements

Problem formulation

Elements of a Literature Review

Writing a Literature Review Resources

literature review and methods

Literature Review Tutorial

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Types of Literature Review

There are many types of literature review. The choice of a specific type depends on your research approach and design. The following types of literature review are the most popular in business studies:

Narrative literature review , also referred to as traditional literature review, critiques literature and summarizes the body of a literature. Narrative review also draws conclusions about the topic and identifies gaps or inconsistencies in a body of knowledge. You need to have a sufficiently focused research question to conduct a narrative literature review

Systematic literature review requires more rigorous and well-defined approach compared to most other types of literature review. Systematic literature review is comprehensive and details the timeframe within which the literature was selected. Systematic literature review can be divided into two categories: meta-analysis and meta-synthesis.

When you conduct meta-analysis you take findings from several studies on the same subject and analyze these using standardized statistical procedures. In meta-analysis patterns and relationships are detected and conclusions are drawn. Meta-analysis is associated with deductive research approach.

Meta-synthesis, on the other hand, is based on non-statistical techniques. This technique integrates, evaluates and interprets findings of multiple qualitative research studies. Meta-synthesis literature review is conducted usually when following inductive research approach.

Scoping literature review , as implied by its name is used to identify the scope or coverage of a body of literature on a given topic. It has been noted that “scoping reviews are useful for examining emerging evidence when it is still unclear what other, more specific questions can be posed and valuably addressed by a more precise systematic review.” [1] The main difference between systematic and scoping types of literature review is that, systematic literature review is conducted to find answer to more specific research questions, whereas scoping literature review is conducted to explore more general research question.

Argumentative literature review , as the name implies, examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. It should be noted that a potential for bias is a major shortcoming associated with argumentative literature review.

Integrative literature review reviews , critiques, and synthesizes secondary data about research topic in an integrated way such that new frameworks and perspectives on the topic are generated. If your research does not involve primary data collection and data analysis, then using integrative literature review will be your only option.

Theoretical literature review focuses on a pool of theory that has accumulated in regard to an issue, concept, theory, phenomena. Theoretical literature reviews play an instrumental role in establishing what theories already exist, the relationships between them, to what degree existing theories have been investigated, and to develop new hypotheses to be tested.

At the earlier parts of the literature review chapter, you need to specify the type of your literature review your chose and justify your choice. Your choice of a specific type of literature review should be based upon your research area, research problem and research methods.  Also, you can briefly discuss other most popular types of literature review mentioned above, to illustrate your awareness of them.

[1] Munn, A. et. al. (2018) “Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach” BMC Medical Research Methodology

Types of Literature Review

  John Dudovskiy

This example shows how a literature review from a PhD thesis can be analysed for its structure, purpose and content.

Three sections of the thesis are analysed to show the:

Access the thesis

Co-witnesses and the effects of discussion on eyewitness memory by Helen M Paterson

Overview of thesis (introduction)

This introductory section is less than two pages long.

The first paragraph:

The other paragraphs describe the content and purpose of each section of the thesis.

Literature review

The literature review is made of up of two chapters.

Chapter 1: Literature review of relevant research

The overall goals of this chapter are to firstly establish the significance of the general field of study, and then identify a place where a new contribution could be made.

The bulk of the chapter critically evaluates the methodologies used in this field to identify the appropriate approach for investigating the research questions.

Chapter 2: Theoretical explanations of memory conformity

Chapter 5, study 3: co-witness contamination.

This chapter has the following structure:

The introduction introduces the particular study to be reported on, and includes a three-and-a-half page literature review.

The literature review in this chapter:

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Research Methods

Literature Review

Literature Review  is a comprehensive survey of the works published in a particular field of study or line of research, usually over a specific period of time, in the form of an in-depth, critical bibliographic essay or annotated list in which attention is drawn to the most significant works.

Also, we can define a literature review as the collected body of scholarly works related to a topic:

The objective of a Literature Review is to find previous published scholarly works relevant to an specific topic

A literature review is important because it:

All content in this section is from Literature Review Research from Old Dominion University 

Keep in mind the following, a literature review is NOT:

Not an essay 

Not an annotated bibliography  in which you summarize each article that you have reviewed.  A literature review goes beyond basic summarizing to focus on the critical analysis of the reviewed works and their relationship to your research question.

Not a research paper   where you select resources to support one side of an issue versus another.  A lit review should explain and consider all sides of an argument in order to avoid bias, and areas of agreement and disagreement should be highlighted.

A literature review serves several purposes. For example, it

As Kennedy (2007) notes*, it is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally that become part of the lore of field. In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature."  Educational Researcher  36 (April 2007): 139-147.

All content in this section is from The Literature Review created by Dr. Robert Larabee USC

Robinson, P. and Lowe, J. (2015),  Literature reviews vs systematic reviews.  Australian and New Zealand Journal of Public Health, 39: 103-103. doi: 10.1111/1753-6405.12393

literature review and methods

What's in the name? The difference between a Systematic Review and a Literature Review, and why it matters . By Lynn Kysh from University of Southern California

literature review and methods

Systematic review or meta-analysis?

A  systematic review  answers a defined research question by collecting and summarizing all empirical evidence that fits pre-specified eligibility criteria.

A  meta-analysis  is the use of statistical methods to summarize the results of these studies.

Systematic reviews, just like other research articles, can be of varying quality. They are a significant piece of work (the Centre for Reviews and Dissemination at York estimates that a team will take 9-24 months), and to be useful to other researchers and practitioners they should have:

Not all systematic reviews contain meta-analysis. 

Meta-analysis is the use of statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review.  More information on meta-analyses can be found in  Cochrane Handbook, Chapter 9 .

A meta-analysis goes beyond critique and integration and conducts secondary statistical analysis on the outcomes of similar studies.  It is a systematic review that uses quantitative methods to synthesize and summarize the results.

An advantage of a meta-analysis is the ability to be completely objective in evaluating research findings.  Not all topics, however, have sufficient research evidence to allow a meta-analysis to be conducted.  In that case, an integrative review is an appropriate strategy. 

Some of the content in this section is from Systematic reviews and meta-analyses: step by step guide created by Kate McAllister.

Readers' Corner

How to write methods section for a literature review

Writing literature reviews is an exciting task; it gives room for creativity and passion for being exposed. This could be the gratification of hard work and dedication for students who study arts-related courses. However, writing literature reviews will be tedious without the right directives and methodology and result in irrelevant and incredible outcomes. There are several methods of writing literature review and how to make your paper the masterpiece you want.

Why is the methodology chapter important?

There are several reasons for maintaining a good process of writing and guidelines that are required. The first reason methodology is important in the literature review is that it is used to sort out points. This is very much needed to avoid jumbling up ideas without directives. With patterns of guides for writing, your research paper will be organized and durable for reading. Students are advised to sort out their ideas and prepare them in paragraphs and lines for easy and efficient understanding.

The methodology is also used for beautifying essays. When ideas and information are placed in descending stages from beginning to end, it makes your paper useful as a secondary source and magnifies how creative you can be.

For a standard academic paper, the use of methodology is implied by workers, students, and educators. It is a standard procedure based on performance score and how well your understanding of the topic is implied. The step-by-step process is essential and is rated by academic rules and guidelines to ensure an acceptable research paper. This is why several students hire professionals on platforms like Edusson to write outstanding papers. These professionals use their skills, knowledge, and time to their advantage and get the job right.

Literature Review Methodology - How to write a methods section for a literature review - 2

What are the parts of a literature review methodology?

Like other forms of writing, a literature review follows a distinct template, a typical intro-body-conclusion, to enhance quality essays. Although, some writers could begin their paper from the middle of the text and work around the plot. However, these are the details of the three known major parts of literature reviews.

The introduction

This is the most important part of a research paper and is also known as the determiner of its worthiness. As a college student writing a review, it is advisable to use a catchy and interesting beginning to attract and sustain the readers’ interest. For example, you may lose interest in a book, an article, or generally a written work because of how it started. That explains how important the introductory paragraph of a research paper is; it states a yes or no opinion of the readers.

This is another essential part of a review. This is the part all ideas, interpretation, opinions, criticism, and actual review is done. You are free to explore all your skills and load off your ideas in this section. However, be careful not to overload content without organizing it properly. You could also give relevant examples and pointers. It is the zone of writing.


The most important part is the conclusion. The conclusion is the summary of ideas given and what your research paper is all about. It is essential not to ignore but to invest in the finishing touch of your research paper. Readers often consult the summary of research papers to know whether it is relevant or useful as material, reference, or review.

Explain your methodological approach

The methodological approach explains how your research paper was written and constructed into finished work. Your paper’s structure , the themes employed, and the organization should be explained in detail. This is not to be mistaken as a review but the stages of procedures resulting in the finished work and the patterns employed. The methodological approach is simply the resources consulted, the editing and proofreading, the style of writing if it was self-done or a third party was employed, whether digital or manual, and how you confirmed your account accuracy and paper integrity. These are some of the examples to explaining what the review process.

Describe your data collection methods

Data collection for research papers is the most complicated and tasking part of writing. It takes a lot of time, energy, and consultations. When writing a literature review, mention the selected source of information and what class your paper can be categorized. You can employ primary or secondary sources as consulted for your given topic. For a topic new in the field, primary sources and the given text could be one of the only few references for research.

There are different data collection methods. Old and classic topics, however, have a lot of materials used. Collection methods could also be categorized as digital or manual. Digital for internet sought materials and manual resources for printed copies. Students also employ oral sources as a source of data collection. There are different categories of collection methods for research papers, be sure to add your method for reference.

Describe your analysis method

Data analysis for research papers and literature reviews is a must need. This is done to confirm your ideas, and to turn data into information, writing process, and research method. It is also relevant to know how unique and standard your paper is. Data could be analyzed by oneself and sometimes in an academic setting by a third party.

The process of converting and conclusion could also be either through qualitative methods, which deal with numbers or words. In a literature review, both methodology are applicable, and evaluations could be made based on a period of the plot, which is a determiner, or the language the writer used for the text topic. The themes could also be a way of evaluation; for example, the dark ages are associated with wars, death, witchcraft, and gothic features. Give details of your research paper evaluation and the student’s sequence that led to the conclusion.

The methodological approach is a major determinant of a literature review and other research papers. It not only states the accuracy of the research but also gives a fine lining to the concluded work. As a student, using a standard approved methodology for literature review is a starter to good performance and a guarantor of being a qualified student in your field of study.

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Types of Reviews

Review Typologies

There are many types of evidence synthesis projects, including systematic reviews as well as others. The selection of review type is wholly dependent on the research question. Not all research questions are well-suited for systematic reviews.

Review the table to peruse review types and associated methodologies. Librarians can also help your team determine which review type might be appropriate for your project. 

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108.  doi:10.1111/j.1471-1842.2009.00848.x

Literature Review: Conducting & Writing

Sample Lit Reviews from Communication Arts

Have an exemplary literature review.

Have you written a stellar literature review you care to share for teaching purposes?

Are you an instructor who has received an exemplary literature review and have permission from the student to post?

Please contact Britt McGowan at [email protected] for inclusion in this guide. All disciplines welcome and encouraged.

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Open Access


Research Article

A systematic review of published literature on mosquito control action thresholds across the world

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization, Writing – original draft, Writing – review & editing

Affiliation Anastasia Mosquito Control District, St. Augustine, Florida, United States of America

Roles Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization, Writing – original draft, Writing – review & editing

Roles Methodology, Writing – review & editing

Roles Funding acquisition, Resources, Writing – review & editing

Roles Conceptualization, Funding acquisition, Methodology, Project administration, Resources, Supervision, Writing – review & editing

* E-mail: [email protected]

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This is an uncorrected proof.

Fig 1

Despite the use of numerous methods of control measures, mosquito populations and mosquito-borne diseases are still increasing globally. Evidence-based action thresholds to initiate or intensify control activities have been identified as essential in reducing mosquito populations to required levels at the correct/optimal time. This systematic review was conducted to identify different mosquito control action thresholds existing across the world and associated surveillance and implementation characteristics.

Methodology/Principal findings

Searches for literature published from 2010 up to 2021 were performed using two search engines, Google Scholar and PubMed Central, according to PRISMA guidelines. A set of inclusion/exclusion criteria were identified and of the 1,485 initial selections, only 87 were included in the final review. Thirty inclusions reported originally generated thresholds. Thirteen inclusions were with statistical models that seemed intended to be continuously utilized to test the exceedance of thresholds in a specific region. There was another set of 44 inclusions that solely mentioned previously generated thresholds. The inclusions with “epidemiological thresholds” outnumbered those with “entomological thresholds”. Most of the inclusions came from Asia and those thresholds were targeted toward Aedes and dengue control. Overall, mosquito counts (adult and larval) and climatic variables (temperature and rainfall) were the most used parameters in thresholds. The associated surveillance and implementation characteristics of the identified thresholds are discussed here.


The review identified 87 publications with different mosquito control thresholds developed across the world and published during the last decade. Associated surveillance and implementation characteristics will help organize surveillance systems targeting the development and implementation of action thresholds, as well as direct awareness towards already existing thresholds for those with programs lacking available resources for comprehensive surveillance systems. The findings of the review highlight data gaps and areas of focus to fill in the action threshold compartment of the IVM toolbox.

Author summary

Many different methods are used and new methods are evolving to control nuisance and vector mosquito populations across the world. Implementation of such control methods at the optimal time has been identified as critical to maintaining the populations below unacceptable levels. The establishment of evidenced-based action thresholds is thus encouraged to achieve maximum results under available resources. This review was conducted to identify different action thresholds published worldwide since 2010 and to understand the associated surveillance characteristics. Only 87 publications filtered through the initial database identification of 1,485 publications were included in the review. Thirty inclusions reported originally generated thresholds, 13 inclusions reported a statistical method with a computable action threshold model, and 44 inclusions mentioned only previously generated thresholds that were used in their study. Overall, the inclusions with thresholds that directly related to disease transmission conditions (“epidemiological thresholds”) outnumbered the inclusions with thresholds that directly related to mosquito abundance. The majority of the thresholds originated in Asia targeting dengue and dengue vectors. The review discusses the associated surveillance characteristics such as the possibility of using external data (previously recorded data), spatial and temporal variations in data used, and the importance of an adequate lead time to initiate control interventions that would help guide to plan better surveillance programs for the development of action thresholds.

Citation: Aryaprema VS, Steck MR, Peper ST, Xue R-d, Qualls WA (2023) A systematic review of published literature on mosquito control action thresholds across the world. PLoS Negl Trop Dis 17(3): e0011173. https://doi.org/10.1371/journal.pntd.0011173

Editor: Olaf Horstick, University of Heidelberg, GERMANY

Received: September 14, 2022; Accepted: February 14, 2023; Published: March 3, 2023

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Data Availability: All relevant data are within the manuscript and its Supporting Information files Data Availability Statement.

Funding: This research project was supported/funded by the Department of the Army, U.S. Army Contracting Command, Aberdeen Providing Ground, Natick, Contracting Division, Ft. Detrick, MD under Deploy War Fighter Protection (DWFP) program W911QY20110004 awarded to AMCD. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.


There are about 3,500 identified mosquito species in different geographic/climatic regions in the world. Some species act as human disease vectors while other species cause only biting nuisance problems. Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually [ 1 ]. More than 80% of the global population is at risk of vector-borne disease, with mosquito-borne diseases (MBDs) being the largest contributor to the human vector-borne disease burden [ 2 ]. MBDs such as dengue, Zika, chikungunya, West Nile virus (WNV), eastern equine encephalitis (EEE), western equine encephalitis (WEE), and malaria cause major public health issues across the world. The global burden of malaria has been estimated to be 219 million cases, with more than 400,000 deaths every year [ 1 ], and a reported 627,000 deaths in 2020 alone [ 3 ]. More than 3.9 billion people in over 129 countries are at risk of contracting dengue, with an estimated 96 million symptomatic cases and an estimated 40,000 deaths every year [ 1 ]. WNV is the most common MBD in the United States [ 4 ]. A total of 21,869 confirmed or probable cases of WNV disease were reported across all 50 states during 2009–2018 [ 5 ]. Chikungunya and Zika have caused the average yearly loss of over 106,000 and 44,000 disability-adjusted life years (DALYs) worldwide, respectively, between 2010 and 2019 [ 6 ]. There is a significant economic burden of MBDs as well. The direct global costs of malaria have been estimated to be at least US $12 billion per year [ 7 ]. The estimated total global cost of dengue was US $8.9 billion in 2013 [ 8 ]. The average cost of WNV in the United States was equivalent to an approximate average of $56 million per year during 1999–2012 [ 9 , 10 ]. There is no specific drug or vaccine available for MBDs such as dengue, chikungunya, etc. [ 11 , 12 ]. Control of vector populations is often the best way, if not the only way, to control the transmission of these diseases. On the other hand, although the major transmission of diseases such as malaria and lymphatic filariasis is controlled by mass drug administration (MDA), the vectors of the diseases are still a human nuisance. For all those reasons, mosquito control is still an integral constituent of the public health infrastructure of many countries.

There are many illustrious instances in history that mosquito control has effectively reduced disease burdens; reduction of malaria in the 1950s-1960s in some countries (in the Americas, Europe and Asia), dengue and yellow fever in the 1950s-1960s in the Americas, dengue in the 1970s-1980s in Singapore and dengue in the1980s-1990s in Cuba [ 13 ]. However, rapid and aggressive changes in mosquito population dynamics imposed by changing influential factors such as the environment, climate, geography, demographics and social culture, have been making mosquito control more challenging in the modern-globalized world. Development of resistance against all major classes of insecticides, and a shortage of effective insecticide innovation, registration, and supply have become another threat to mosquito control [ 14 ]. Compounding all those complexities, mosquito control is often reactive [ 14 ] as it is implemented only in direct response to already increased risk based on vector or disease surveillance results in the present time [ 15 ]. The effects of such control programs would be too late to prevent undesirable levels of human-mosquito contact, and thus the potential for disease explosions. One of the key elements lacking in many mosquito control programs is the use of reliable preemptive indicators to initiate proactive control operations before mosquito populations or disease risks are elevated to undesirable levels. It is widely accepted that Integrated Vector Management (IVM) and Integrated Mosquito Management (IMM) programs that make reliable evidence-based control decisions and that utilize appropriate control tools, can effectively reduce mosquito abundance and disease risk [ 16 ]. Therefore, early warning systems with evidence-based action thresholds that trigger interventions at the optimal time are now becoming critical in operational mosquito control. In addition to being more effective in controlling mosquito populations, such systems would help ensure prioritized allocation of resources, manage insecticide resistance, and hence help manage overall program logistics.

Understanding the relationship between influential factors and the dynamics of mosquito populations and disease transmission through properly planned surveillance systems is fundamental in establishing evidence-based mosquito control action thresholds. The structure of surveillance systems and therefore the data collected by different mosquito control programs are widely varied due to differences in geography, climate, economy, and other logistic factors. Therefore, there could be different action thresholds for the same species or species groups in different geographic/climatic regions as well as in the same region. Given the critical importance of the use of action thresholds in mosquito control, we systematically reviewed the published literature to identify different mosquito control action thresholds existing across the world and associated surveillance and implementation characteristics. The findings will give insights to mosquito control program managers and others, who anticipate developing and establishing their own action thresholds, to plan appropriate surveillance programs. Otherwise, this review will be helpful for those that wish to utilize already developed action thresholds due to the inability to establish comprehensive surveillance systems, especially the routine collection of mosquito data.

The systematic review was conducted following the PRISMA 2020 guidelines [ 17 ]. A protocol was prepared and agreed upon by all authors. An appropriate literature search was conducted from March 2020 to July 2021 using two main public search engines, Google Scholar (GS) and PubMed Central (PMC). The search terms were chosen to encompass a broad range of major vector species, diseases, surveillance/threshold measures, and analogies for “threshold”. Primary search queries involved various combinations of key terms using (i) major vector mosquito genera (“ Anopheles ”, “ Aedes ”, “ Culex ”), followed by AND “mosquito” AND “[] threshold” ([]: risk, epidemic, disease, tolerance, action), (ii) [(disease name) control” (disease name: malaria, dengue, zika, chikungunya, West Nile virus) followed by AND “threshold” /”action threshold”. (iii) “mosquito control”, “mosquito abundance”, “evidence based” with “threshold”/“action threshold”/”tolerance threshold”, and (iv) “control” followed by AND “mosquito” AND some analogous “threshold” terms that were discovered at the initial planning and search stage such as “trigger”/“warning”. For GS searches, all key terms were put in quotation marks to ensure a feasible number of search results (i.e. no more than several hundred). Quotation marks were also used for PMC searches; however, several PMC searches were conducted without quotation marks to instead broaden the search net after receiving any output of “no results found”. Searches were independently conducted by two human reviewers (VSA, MRS) with separate search terms until all planned combinations were exhausted and no new links appeared on the first listed page of results, considered as our point of saturation. Search process and the inclusion/exclusion criteria are summarized in Fig 1 . Any disagreement at each stage was resolved by in-person discussions.



Direct control thresholds/operational targets to keep mosquito populations below unaccepted levels of biting nuisance or disease transmission, risk level indicators to guide mosquito control, defined pest levels, and indicators of seasonal mosquito activity were identified as mosquito control action thresholds in this review. Retrieved publications were divided into three inclusion categories to reflect the various circumstances an action threshold was implicated in them; (i) “generated thresholds”- publications with an originally generated action threshold, (ii) “generated-models”—publications with a statistical model that involved a computable trigger/risk assessment with input of dynamic data to indicate if the area under study is over a threshold or within a risk level, and (iii) “mentioned thresholds”–publications with clear mention of a previously generated action threshold/s when the cross-references cited in them were not eligible to be included in (i) or (ii). Within those three categories, two types of action thresholds were identified: “entomological thresholds”- the threshold directly indicates mosquito abundance without connecting it to an epidemiological indication (EI) of a disease (could be associated with either vectors or non-vector nuisance mosquitoes), and “epidemiological thresholds”- the threshold is directly related to an EI (transmission, outbreak, epidemic). Calculation methods of EIs greatly differed between publications, some calling for flexibility dependent on the choices of local government bodies, others using specific calculations. Definitions for EI that were defined and/or justified in publications are included alongside action threshold descriptions in supplemental data tables ( S1 , S2 and S3 Tables). Other data points extracted during the full-text screening included publication type (scientific journal, guidelines, theses/dissertations, etc., geographic origin of the threshold/s (continent, climatic region), spatial unit of analysis (study area size), spatial unit of implementation (suggested/planned area associated with threshold), origin of data (self-sampled data, previously recorded data), time span of used data, data frequency (temporal resolution used data), mosquito species in concern, disease in concern, variables used in the threshold, types of mosquito data (e.g. larval indices, adult trap counts), data frequency, associated proactive lead time from the exceedance of the threshold to its indication, self-assessment of the validity of the threshold, and intended use of the threshold.

GS and PMC produced 1,559 and 2,322 search results, respectively, between the two human reviewers and search query combinations. The quantitative value of unique search results was revealed by the removal of replicates through the compilation of all citations from recorded search queries. Replicate overlap between the two search engines was minimal and the total number of initial unique search manually screened for abstracts was 1,485. The abstract screening reduced the initial unique 1,485 publications to 233 publications for the next screening (i.e., reading the full text) and data extraction process. Combined with the 4 cross-references of “mentioned thresholds” which met all the inclusion criteria, the final screening identified 87 publications to be included in the review (inclusions, hereafter) ( Fig 2 ).



There were 30 inclusions with “generated thresholds” (hereafter GTs, S1 Table ) [ 18 – 47 ], 13 inclusions with “generated-models” (hereafter GMs, S2 Table ) [ 48 – 60 ], and 44 inclusions with “mentioned thresholds” (hereafter MTs, S3 Table ) [ 61 – 104 ]. Some of the MTs were evidence-based generations of previously (before 2010) published studies while a few did not discuss how they were generated. As per the respective inclusions, they were still in use and therefore, worthwhile looking into available relevant data points. Outcomes of extracted data points were presented as percentages of all inclusions or GTs/GMs and MTs as appropriate.

1. Publication type

The majority of inclusions were retrieved from scientific journals (89.7% [78/87]) [18–47 (GT); [ 48 – 59 ] (GM); 61–96 (MT)] and there were three program guidelines (3.4% [3/87]) [97–99 (MT)], three technical reports (3.4% [3/87]) [100–102 (MT)], two conference proceedings (2.3% [2/87]) [103,104 (MT)], and one thesis/dissertation (1.1% (1/87)] [60 (GM)].

2. Geographic origin of the threshold

Inclusions with thresholds were identified in broadly defined two climatic regions: tropical/sub-tropical (71.3% [62/87]) [18–44 (GT);49,51–60 (GM); 61,64,65,67,69,71,75,76,77,80,82,83,85,87–90, 92–98 (MT)], and temperate (24% [21/87]) [45–47 (GT); 48,50 (GM); 62,63,66,68,70,72–74,78,86,99–104 (MT)]. There were a few inclusions (5.7% [5/87]) that reported (i) a threshold developed from data of different climatic regions [48 (GM)], (ii) different thresholds from different regions [81 (MT)], and (iii) those that did not specify the geographic origin of the threshold [79,84,91 (MT)].

The highest number of inclusions were from Asia (36.7% [32/87]) [22–27,29,30,33–38,41–44 (GT); 56–59 (GM); 71,75,77,82,85,87,89,90,93,98 (MT)], followed by North America (27.5% [24/87]) [28,45,46 (GT); 48–51 (GM); 61–63,68,70,72,74,78,80,83,86,92,96,97,99,103,104 (MT)], and South America (14% [12/87]) [19,40 (GT); 52–55 (GM); 64,65,67,69,75,81 (MT)].

3. Threshold types and epidemiological indication (EI)

The majority of inclusions reported “epidemiological thresholds” (77% [67/87]) [20–44 (GT); 49–60 (GM); 61–65,67,69,71,73,75,76,77,79,81–84,87–91,93–95,97,98,101–104 (MT)], while only 19 inclusions reported “entomological thresholds” (21.8% [19/87]) [18,19,45–47 (GT); 48 (GM); 66,68,70,72,74,78,80,85,83,86,96,99,100 (MT)]. There was one inclusion that reported both types (1.1% [1/87]) [92 (MT)].

Disease transmission was the expected EI of most of the “epidemiological threshold” inclusions (56% [38/68]) [27–35,38,39,42–44 (GT); 50,55,58,59 (GM); 62,63,65,67,69,73,75,76,79,81,87,89,90–95,98,101 (MT)] followed by epidemics (28% [19/68]) [20,21,24,41 (GT); 49,52–54,57 (GM); 48,71,77,82,84,88,97,102–104 (MT)] and outbreaks (14.7% [10/68]) [22,23,26,36,39,40 (GT); 51,56,60 (GM); 64 (MT)]. There was one inclusion that reported thresholds for both disease transmission and outbreaks [25 (GT)]. However, it is noteworthy that the definition of the EI of those thresholds could be greatly varied between different inclusions.

4. Targeted mosquito species and diseases

Aedes aegypti Linn. and/or Aedes albopictus Skuse were the most reported mosquito species (80.5% [71/87]) [18,19,21–28,30,31,33–36,38–44,47 (GT); 49–60 GM), 61–64,66–71,73,75–95,98,99,102 (MT)]. Twelve inclusions mentioned Culex species (13.8% [12/87]) [20,29,45,46 (GT); 48 (GM); 63,72,74,97,100,103,104 (MT)] and two inclusions reported thresholds for Anopheles species (2.3% [2/87]) (32 GT); 101 (MT)]. Other Aedes species were considered in five inclusions (5.7% [5/87]) [20 (GT); 48 (GM); 79,94,100 (MT)]. There were four inclusions (4.6% [4/87]), three “epidemiological thresholds” [37 (GT)]; 62,65 (MT)] and one “entomological threshold” [96 (MT)] that did not specify any mosquito species.

In parallel with the most reported mosquito species, dengue was the most reported disease (61% [53/87]) [19,22–27,30,33–36,38–44 (GT); 51–60 (GM); 61,64,65,67,69,71,73,75,-77,79,82,84,87–91,93–95,98,99,102 (MT)] followed by chikungunya (10.3% [9/87]) [21,28,31 (GT); 73,81,83,95,99,102 (GM)] and Zika (9.2% [8/87]) [49,50 (GM); 80,81,88,92,95,102 (MT)]. There were eight inclusions for WNV (9.2% [8/87]) (45,46 (GT); 62,63,74,97,103,104 (MT)], three for malaria (3.4% [3/87]) [32,37 (GT); 101 (MT)], two for yellow fever (2.3% [2/87]) 79,91 (MT)], two for Ross river virus (RRV) (2.3% [2/87]) [20 (GT); 100 (MT)], one for Japanese encephalitis (1.1% [1/87]) [29 (GT)], and one for other viral diseases (1.1% [1/87]) [100 (MT)]. Eleven “entomological threshold” inclusions did not specify any disease (12.6% [11/87]) [18,47 (GT); 48 (GM); 66,68,70,72,78,85,86,96 (MT)].

5. Variables used in action thresholds/model inputs

Different studies have used different variables to generate thresholds. Mosquito data were the most used (63.2% [55/87]) [21–26,28,30,31,35,36,38,41,43,44 (GT); 55,59 (GM); 61,64,66–89,91–96,98–101,103,104 (MT)] and most of those thresholds were for Ae . aegypti and/or Ae . albopictus for the control of dengue (63.6% [35/55]) [22–26,30,35,36,38,41,43,44 (GT); 55,59 (GM); 61,64,67,69,71,73,75–77,79,82,84,87–89,91,93,94,95,98,99 (MT)], chikungunya (14.5% [8/55]) [21,28,31 (GT); 73,81,83,95,99 (MT)], Zika (9% [5/55]) [ 80 , 81 , 88 , 92 , 95 ], yellow fever (3.6% [2/55]) [ 79 , 91 ]. Some of the MTs used mosquito data for thresholds of WNV (5.5% [3/55]) [ 74 , 103 , 104 ], malaria (1.8% [1/55]) [ 101 ], RRV and other diseases (1.8%) [1/55]) [ 100 ]. Larval indices (Stegomyia indices- Breteau index, house index, and container index) were the most used mosquito data variable (41.8% [23/55]) [23–26,30,35,36,41,43 (GT); 61,64,71,77,79,82,84,87,88,89,91,92,94,95 (MT)] followed by adult mosquito trap counts (31% [17/55]) [28,44 (GT); 66–68,70,78,80,81,83,86,96,99–101,103,104 (MT)]. The presence of larvae (9% [5/55]) [38 (GT); 59 (GM); 72,74,92 (MT)], pupal index (3.6% [2/55]) [ 69 , 75 ], presence of eggs/egg density (11% [6/55]) [21,31 (GT); 73,76,85,93 (MT)], biting density (1.8% [1/55]) [27 (GT)], resting density (1.8% [1/55]) [24 (GT)], and virus screening (1.8% [1/55]) [55 (GM)] were the other mosquito data variables used. Two other GMs [ 48 , 58 ] used mosquito data only for the development of their climate-based risk prediction models while all other GMs entirely disregarded mosquitoes as either model parameters or output in the development of models.

All the GT “entomological thresholds” and all except Ong et al. [ 59 ] of GMs primarily relied on climate variables while none of the MTs reported the use of climate data. Thirty percent of all inclusions (30% [26/87]) [18–20,27,29,32–34,37,39,42,45–47 (GT); 48–58,60 (GM)] used climate variables, mainly temperature (88.5% [23/26]) [18,19,25,27,29,33,39,42,45–47 (GT); 48–58,60 (GM)] and rainfall (53.8% [14/26]) [20,32,34,37,45,46 (GT); 48,52–54,56–58,60 (GM)]. One of those studies [25 (GT)] reported thresholds with several climatic variables; temperature, relative humidity (RH), wind speed, and sunshine duration, and another [57 (GM)] used RH in the final model.

Fifteen of all inclusions (17.2% [15/87]) [40 (GT); 49, 51–57,59,60 (GM); 63,65,90,102 (MT)] used human case data in their thresholds/model inputs with indications of preemptive use of the threshold.

In addition, two inclusions discussed the use of a special index of several variables [63,97 (MT)], and another one used the number of dead birds [62 (MT)]. Geographic location was important in several GMs; Foley and Pecor [ 50 ] relied on geo-referencing US military facilities onto published vector and virus habitat suitability maps, while Lowes et al. [ 52 – 54 ] compartmentalized risk to micro-region resolution in Brazil with environmental variables of biome and altitude. One GM that involved spatial environmental parameters in creating risk maps used vegetation, connectivity, and residential coverage [ 49 ] while another used terrain height [ 58 ]. Zhang et al. [ 57 ] stood out because the climate and epidemiological surveillance parameters of one city were modeled to predict the extension of disease transmission risk to a neighboring city. There was a unique GM that approached utilizing social media platform data -Twitter tweets [ 55 ].

6. Statistical procedures used in GMs

All GMs incorporated a threshold as the dividing value for a binary classification system, i.e., the model output—estimated mosquito count [ 48 ], estimated disease cases [ 51 – 54 , 56 , 57 , 59 , 60 ], probability of epidemic/outbreak [ 49 ], probability of exceeding a defined number of disease cases [ 51 – 54 ] that will trigger a warning if the estimate exceeds the binary divider value and thus the area enters a higher category of risk. Some studies involved two or more binary classification schemes that led to multiple risk warning categories (38.5% [5/13]) [ 50 , 52 – 54 , 59 ]. Most studies (61.5% [8/13]) directly stated a specific number or rate of disease cases as their chosen EI [ 51 – 57 , 60 ].

The models vary in complexity and the majority (69.2% [9/13]) involved a generalized linear model or generalized linear mixed model [ 48 , 51 – 58 ]. A common paradigm was to develop a model that predicted the Y% probability of exceeding the X number of disease cases (i.e., EI). Comparatively, Foley and Pecor [ 50 ] created an excel spreadsheet calculator that entailed a monthly review. It ranked Zika transmission risk based on the temperature and habitat suitability of virus and mosquito vectors, meaning four separate binary classifications had to be performed to determine the (forecast) final risk code status for the upcoming month. Other studies utilized Random Forest machine learning [ 59 , 60 ] or developed a risk-assessment framework involving stochastic simulations [ 49 ]. A series of inclusions of the same author group detailed the advancing development of a Bayesian spatio-temporal hierarchical model to predict dengue risk in Brazil by microregion [ 52 , 53 ], later tailored to proactively forecast risk for the 2014 World Cup [ 54 ], and finally validated after the tournament’s conclusion [ 64 ]. The advanced model was also implemented for the island country of Barbados [ 51 ]. Interestingly, the advanced model incorporated a pre-defined threshold of cases and a probability threshold that could be optimized to reduce false warnings while aiding policymakers to effectively allocate control resources and activities, a priority also discussed in another GM [ 49 ].

7. Surveillance and implementation characteristics

Associated surveillance and implementation characteristics reported by GTs/GMs (n = 43) were analyzed. Analysis of MT data were included whenever available. Species-wise analysis was not appropriate due to the very low number of inclusions of other species except Ae . aegypti/Ae . albopictus (80% [36/43]). Hence the analysis was conducted collectively for all inclusions.

a. The origin and time span of data.

The origin of data used to generate action thresholds varied in different inclusions. All except one inclusion (97.7% [42/43]) used external data sources (previously recorded data) for at least one variable used. Thirty studies (69.8% [30/43]) relied exclusively on external data sources [20, 22–24,27,29,30,32–34,37–40,42–46 (GT); 49–54, 56–60 (GM)] while 13 studies (30.2% [13/43]) [18,21,25,26,28,31,35,36,40,41,47 (GT); 48,55 (GM)] collected self-sampled data. All the self-sampled data were on mosquito data of which 3 collected virus screening data (23% [3/13]) [28,47 (GT); 55 (GM)] and one collected climate data (7.7% [1/13]) [47 (GT)] as well. External data were retrieved on human cases (67.4% [29/43]) [20,23–27,29,30,32,33–39,41,42,44 (GT); 49,51–59 (GM)], climate variables (65% [28/43]) [18–21,24,27–34,37,39,45,46 (GT); 48,50–58,60 (GM)], mosquito data (30.2% [13/43]) [22–24,35,38,41,42,44–46 (GT); 55,58,59 (GM)], and other data such as demographic data, spatial data, tweets (37.2% [10/43]) [49–51,53–55,57–60 (GM)].

More than half of those inclusions (52.2% [23/43]) used >5 years’ data [20,24,27,29–33,35,38–42 (GT); 49,51–54,56,57,59,60 (GM)] with half of them (50% [12/24]) used >10 years’ data [20,29,30,32,38,40 (GT); 49,51,54,56,57,60 (GM)]. Seven studies used 2–5 years’ data (16.3% [7/43]) [34,36,37,46,47 (GT); 48,54 (GM)] and 12 studies (28% [12/43] used data spanning less than two years [18,19,21–23,26,28,31,43,44 (GT); 50,58 (GM)]. The majority of MTs originated before 2010 (52.3% [23/44]) [ 61 – 65 , 67 – 69 , 71 , 75 , 76 , 79 , 81 , 82 , 84 , 87 , 88 , 89 , 91 – 93 , 95 , 100 , 104 ] while the time of origination was not clear in other MTs.

b. Data frequency.

The majority of GTs and GMs that used mosquito data relied mostly on daily/weekly data (35.3% [6/17]) [21,23,28,31,44 (GT); 55 (GM)] or bi-weekly/monthly data (35.3% [6/17]) [24,25,30,35,36,41 (GT)]. Two inclusions used yearly data (11.8% [2/17]) [38 (GT); 59 (GM)], one inclusion used only one-time data to generate action thresholds for two city parks (6% [1/17]) [22 (GT)], and there were two inclusions with no clear mention of the data frequency (11.8% [2/17]) [26,43 (GT)]. Inclusions that used climatic variables relied mostly on daily/weekly data (61.5% [16/26]) [18,19,27,33,34,42,45–47 (GT); 48,49,55–58,60 (GM)] over monthly data (38.5% [10/26]) [20,29,32,37,39 (GT); 50–54 (GM)]. Daily/weekly data frequency was the most used (50% [5/10]) [49,55–57,60 (GM)] in GTs and GMs that used human case data.

c. Spatial unit of analysis and intended spatial implementation of thresholds.

The spatial assessment level (data collection units) of GTs/GMs varied from 1x1 km grid cells in neighborhoods to district blocks, to represent the same or larger spatial units of analysis (study area). Town/city (28% [12/43]) [21,24,27,30,33,40,44 (GT);55–57,59,60 (GM)], country (14% [6/43]) [29,32,42 (GT); 51,52,54 (GM)], municipality (9.3% [4/43]) [18,25,26,47 (GT)], district (9.3% [4/43]) [23,36,37,43 (GT)], and region (9.3% [4/43]) [34,45,46 (GT): 53 (GM)] were the most studied spatial units of analysis.

Those thresholds were generated with the intention of implementing them in the study area itself (69.7% [30/43]) [22,23,25–27,29,31–34,36–46 (GT); 49–51,54,56–60 (GM)] or a larger area including the study area (28% [12/43]) [18,19,21,24,28,30,35,47 (GT); 48,52,53,55 (GM)]. Only one inclusion intended to implement the threshold in a smaller area than the study area (2.3% [1/43]) [20 (GT)].

More than half of the MTs (66% [29/44]) [ 61 – 65 , 66 – 68 , 70 , 72 – 74 , 76 – 78 , 80 , 83 , 85 – 87 , 89 , 90 , 93 , 96 , 97 , 100 , 101 , 103 , 104 ] mentioned thresholds that originated in the same country or at least in the same region [ 102 ] and of these, nine originated from the same individual state within the United States [ 63 , 68 , 72 , 74 , 78 , 86 , 96 , 97 , 103 ]. Eight inclusions (18.2% [8/44]) [ 66 , 78 , 86 , 90 , 96 , 100 – 102 ] mentioned thresholds that originated from the same program. One inclusion (2.3% [1/44]) [ 75 ] mentioned a threshold with a different country origin while four inclusions (9% [4/44]) [ 69 , 88 , 92 , 94 ] mentioned thresholds from different continental regions. Only one inclusion (2.3% [1/44]) [ 81 ] mentioned different thresholds either with the same country origin or different country origin and one inclusion (2.3% [1/44]) [ 98 ] did not cite a cross-reference or mention the origin of the mentioned threshold. Globally recognized thresholds were mentioned in six inclusions (11.4% [5/44]) [ 71 , 79 , 84 , 91 , 95 ].

d. Lead time and validation of the threshold.

The most reported lead time that used mosquito data (41.2% [7/17]) [24,30,35,36,41,44 (GT); 55 (GM)], as well as climate data (46.2% [12/26]) [20,27,33,37,39,42,45 (GT); 51,54,55,57,60 (GM)], was 1–3 months. Three inclusions with mosquito data (11.8% [2/17]) [24 (GT); 55 (GM)] and three inclusions with climate data (11.5% [3/26]) [18 (GT); 55,58 (GM)] reported 1–3 weeks lead time. Using climate data, four other inclusions (15.4% [4/26]) [52,53,56,57 (GM)] reported a lead time of more than 3 months while Smith et al. [32 (GT)] reported a different lead time. However, ten mosquito data inclusions (58.8% [10/17]) [21–23,25,26,28,31,38,43 (GT); 59 (GM)] did not report any lead time. Notably, several GMs utilized or made suggestions to utilize a specific climate forecasting resource to optimize the proactive lead time for control interventions [ 50 – 54 ]. Others developed models that used climate data at time points prior to the time point of model predictions, although lead-time would only be as long as the shortest time-lagged variable [ 49 , 56 , 57 ].

Most inclusions (60.5% [26/43]) analyzed performance statistics for GT/GM validation purposes. Of those, the majority used only training data (57.7% [15/26]) [20,23–25,27,31,32,38,40,41,45 (GT); 51,52,54,57 (GM)] while only eleven inclusions (42.3% [11/26]) [21,36,43,46 (GT); 48,53,55,56,58–60 (GM)] used testing data worth 6 weeks to 5 years. Of all GTs/GMs seventeen (39.5% [17/43]) [18,19,22,26,28–30,33–35,37,39,42,44,47 (GT); 49,50 (GM)] did not report on validation of GT/GM performance. However, some of those GTs were validated in subsequent studies which were included in the review as MTs [ 61 – 65 ].

8. Intended use of the threshold

Two broad categories of intended uses were identified from the inclusions. Direct intentions included those that stated direct utility for initiating mosquito control operations by setting an operational target threshold to keep populations below unaccepted levels of biting nuisance/disease transmission and others that determined different risk levels to guide a mosquito control response and/or effective resource allocation. Indirect intentions involved inclusions that mentioned mosquito/vector control at least once but discussed the utility of the action threshold within the wider expanse of a public health response without a specific discussion of focused implementation in mosquito control.

The majority of inclusions (88.5% [77/87]) [18–23,25–28,31,34–36,38,40–47 (GT); 48,50,52–60 (GM); 61–64, 66–104 (MT)] indicated the direct use of the threshold in mosquito control. Seven inclusions (11.5% [10/87]) 24,29,30,32,33,37,39 (GT); 49,51 (GM); 65 (MT)] intended to use the thresholds in initiating or guiding public health responses to control disease spread indirectly indicating their use in mosquito control.

Although the establishment of action thresholds has become critically important to achieve the maximum cost-effective benefit of mosquito control interventions, there is no formulated guidelines on the development of thresholds in different environmental settings. This review attempted to identify publications with mosquito control action thresholds across the world during the last 10 years and the basic surveillance and implementation characteristics associated with those thresholds. We hope the findings of the review will help guide mosquito control program managers and any other personnel who are interested in developing/using action thresholds to be included in their programs.

The 87 inclusions of the review were categorized into three broad categories; originally generated thresholds, generated models, and mention of previously generated thresholds. General information and surveillance/implementation characteristics of the three categories were examined to understand the structure of their surveillance systems.

More than 90% of the inclusions were from scientific journals/conference proceedings indicating the scientific/academic interest on developing action thresholds. However, the very low number (6.8%) of inclusions from program guidelines/technical reports could not be considered due to the scarcity of thresholds being used practically in mosquito control programs. There could be established thresholds that have already been in the specific IMM toolboxes of mosquito control programs but not disseminated in publications or in publications that fall into our inclusion criteria. We have planned and already initiated to identify those action thresholds through individual discussions with program managers/authorities in another study.

Overall, 77% of identified thresholds were “epidemiological thresholds and thus, indicate that the need to establish mosquito control action thresholds has been driven mainly by the transmission dynamics of mosquito-borne diseases rather than by biting nuisance. The majority of epidemiological thresholds here were to indicate transmission of disease although there is a chance of overlapping as the used epidemiological indication terms were not based on strict definitions. It is evidence for the need of more promising proactive mosquito control as discussed by Eisen et al. [ 105 ] rather than waiting for the transmission to transform into outbreaks or epidemics. Although mosquitoes are widely distributed in different climatic regions in the world, they thrive in regions with warm temperatures, humid conditions, and high rainfall, and thus tropical and sub-tropical areas are ideal for their survival [ 106 ]. Most of the identified action thresholds (>70%) being generated in tropical and sub-tropical climatic regions indicate their relevance to the burden of mosquitoes and mosquito-borne diseases in those regions, compared to others. The fact that the highest number of thresholds, were originated in Asia and associated most with dengue and dengue vectors should have a link with recent increases in the incidences of major dengue outbreaks and epidemics reported mainly in the Asian region [ 107 , 108 ]. However, recent studies show the geographical distribution of Ae . aegypti and Ae . albopictus is now extensive in all human inhabited continents; Europe and North America [ 109 ], South America [ 110 ], Oceania [ 111 , 112 ], and Africa [ 113 ].

Overall, the majority of inclusions have used mosquito data in thresholds. However, some of the recently developed entomological thresholds have moved on to use climate data, mainly temperature, rather than using mosquito data itself as done previously (before 2010). It is a good step forward to proactively inform the need to initiate mosquito control and thus help bring about more effective prevention of unacceptable levels of mosquito abundance. Despite controversy on the association with the number of disease cases [ 36 , 41 , 114 – 122 ], the majority of epidemiological thresholds for dengue and chikungunya were generated using Stegomyia larval indices.

The data collection duration is a substantial characteristic in the process of action threshold development. A sufficient time span would allow identifying any time sensitive variations in the identified correlations, thus in the generated action thresholds. Therefore, thresholds developed using historic data would be more reliable than those generated using only current data or one-time data. Davis et al. [ 123 ] suggested the inconsistent reliability and questionable validity of the thresholds generated in the study by using <3 years data would be refined with additional years of data. Using <5 years’ historic data in their study, Bowman et al. [ 124 ] suggested that data of a greater number of historic years would have generated more reliable results. Other studies which reported alert thresholds for malaria based on disease case numbers discuss the need of at least 5 years of historical data [ 125 , 126 ]. The majority of studies reviewed here being used carried out over more than 5 years have allowed the possible temporal variations to be considered and compromised. Studies conducted in less than 2 years might not be able to catch time sensitive variations in the variables used thus making the threshold less reliable to use over the years. Likewise, mosquito abundance and disease transmission dynamics may change over time due to many reasons such as environmental/climatic changes, human mobility, etc. Most of the “mentioned thresholds” being developed more than ten years ago might need assessments and necessary updates before using in current mosquito control programs. Notably, almost all identified studies have used external data sources mainly from relevant government entities to generate thresholds. The use of external data sources requires careful selection and matching of data in the temporal and spatial units in concern to generate reliable thresholds. The distribution of mosquitoes and hence the mosquito-borne diseases are clustered in nature based on different ecological niches they use [ 127 ]. However, the demarcation of spatial units of those studies is based on man-made administrative boundaries rather than on ecological or geographical determinants. Therefore, the use of a particular action threshold in the spatial unit of its origin is more reasonable than using it in an area with different geographical, climatic, environmental, demographic, socio-economic, and other relevant characteristics. Stegomyia house index (HI) of less than 1% indicates no risk of a dengue outbreak in Brazil [ 128 ] but outbreaks occurred in Singapore when the national overall HI was less than 1% [ 129 ]. Researchers have shown that the geographical level heterogeneity affects the performance of thresholds with the thresholds developed for smaller units performing best [ 120 ]. The thresholds varied among different spatial units such as different districts in the same country [ 37 , 41 ] as well as among different climatic zones in the same country [ 39 ]. Romiti et al. [ 130 ] report a significant difference in Ae . albopictus development threshold temperature among municipalities. In contrast, some studies report the same threshold for the seasonal emergence of Ae . albopictus in two countries [ 18 , 47 ]. Bowman et al. [ 124 ] report the predictive ability of certain meteorological and epidemiological alarm variables of dengue across all countries studied. Hence, there could not be universally reliable thresholds and there is no definitive fact that the same threshold cannot be used elsewhere. The majority of the publications analyzed here have action thresholds intended to be used in the same spatial unit as its origin. However, locations with similar determinant characteristics but yet unable to collect required surveillance data would need to consider using an already developed appropriate threshold after confirming with initial environmental assessments/validations.

Temporal resolution of data collection and analysis plays an important role in the development of reliable action thresholds. Smaller scale resolutions (e.g. weekly data) would reveal more precise relationships between variables compared to higher scale resolutions (e.g. monthly/yearly data) [ 131 ]. Realistically, the available resources and other logistics will be deterministic factors of the temporal resolution of data collection. However, most of the studies included in this review achieved at least a monthly resolution.

One of the main purposes of establishing mosquito control action thresholds is to provide sufficient time for planning, organizing, and implementing appropriate control activities at the optimal time. Sufficient lead time from the established threshold to the exceedance of its indication would help mosquito control program managers to plan, organize and implement appropriate control measures for effective reduction of mosquito populations. Entomological thresholds seem to have shorter lead time (mentioned in only 2 studies) than epidemiological thresholds. Epidemiological thresholds which used climatic variables have longer lead times than those using mosquito data variables. Hii et al. [ 132 ] discuss the importance of the optimal lead time which would give sufficient time for successful implementation of mosquito control. They suggest that an average of 2 months with maximum 3 months lead time is typically required for effective mitigation of dengue transmission in Singapore in both non-epidemic and epidemic years. The development of a reliable mosquito control action threshold/s is a very complex process due to the interplay of several tangential factors, such as frequency and amount of virus importation, and herd immunity [ 133 ] and human-mosquito contact rates [ 134 ]. However, those thresholds should be accurate enough not to provide too many false warnings which would lead to issues such as wastage of resources and development of insecticide resistance. Validation of generated thresholds is important before establishing to confirm their performance in operational settings. Validation studies have confirmed the effectiveness of thresholds generated in the same study [ 36 ] as well as previous thresholds [ 49 ]. After field validation of previous thresholds by Sanchez et al. [ 120 ], the performance of overall neighborhood Breteau Index (BI) ≥ 1.3 was denied and the most straight forward performance of BI max ≥ 4 was confirmed as an indicator for predicting dengue transmission [ 48 ]. MacCormack-Gelles et al. [ 51 ] showed that the HI threshold imposed by the Brazilian Ministry of Health was not in compliance with increasing dengue risk in Fortaleza, Brazil. Most of the thresholds included in this review still need to be field validated, before establishing to inform the need of initiation of mosquito control activities.


Pertaining to the restrictions of available time and resources, the systematic review has several limitations which might have eliminated some important publications: (i) the literature search was limited only to two search engines (Google scholar and PubMed), (ii) the search was limited to 2010–2021, (iii) language restricted to English only, and (iv) grey literature not used.


Supporting information

S1 checklist. prisma checklist for abstracts..


S2 Checklist. PRISMA checklist.


S1 Table. Generated mosquito control action thresholds (“generated thresholds”) found in publications included in the review.


S2 Table. Generated models for mosquito control action thresholds (“generated-models”) found in publications included in the review.


S3 Table. Mentioned mosquito control action thresholds (“mentioned thresholds”) found in publications included in the review.



The authors acknowledge all the support by Anastasia Mosquito Control District, St. Augustine, Florida.

How to Write a Stellar Literature Review

Lindsay Kramer

When you’re conducting academic research, a literature review is a survey of the scholarly sources you’ve consulted in your research. Typically, literature reviews are only necessary when you’re doing a significant academic project, such as a dissertation, research paper, or a  thesis . For shorter pieces of academic writing, including essays , your works cited page is sufficient. 

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When would I write a literature review?

As we mentioned above, writing a literature review is part of writing an academic paper. The purpose of writing a literature review is to present the  sources you’ve used in your research to your work’s readers. By doing this, you’re communicating several things:

Writing a literature review is no small undertaking! But then again, neither is writing your thesis, dissertation, or even a lengthy, comprehensive research paper. 

In many cases, you’re required to write a literature review and submit it to your academic supervisor before getting started on your paper. This gives your supervisor the opportunity to see what you’re researching, how you’re conducting that research, and, if necessary, provide feedback and suggestions to make your research stronger. This could mean suggesting alternative sources or redirecting your research’s scope.

A literature review is not the same thing as an  abstract . Both are critical parts of a research project, but while an abstract summarizes your work, a literature review summarizes the research you conducted to complete your work. In many cases, an abstract’s goal is to engage readers and help researchers and cataloguers determine whether your work is a relevant source for their work and whether it’s a good fit for a specific collection or academic journal. A literature review’s goal is to provide a “behind the scenes” look at how you did your research, underpinning it as a valid piece of scholarly research. 

How to write a literature review

Literature review structure.

A literature review is  structured similarly to an essay . It begins with an introduction that states the research question and explains how you tackled it. Following are body paragraphs that explain your research in further detail. Then, it ends with a conclusion section that reiterates the research question while summarizing the insights you had through your research. 

A literature review’s length depends largely on the type of research it’s being written for. For a short paper, it might only be a few pages long, but for a lengthy work like a thesis or dissertation, it’s often an entire chapter. 

Literature review style

A literature review requires the same style as any other piece of  academic writing . That means no contractions or colloquialisms, concise language, formal tone, and an objective perspective at all times. 

To distinguish between your analysis and prior scholarly work in the field, use the past tense when discussing the previous research conducted on your topic and the present tense when discussing your point of view. For example, you might write that a specific author conducted research or that they had been influenced by earlier researchers in the field, but also that you are exploring different research methods and that you are posing certain questions. 

Writing a literature review, step-by-step

Define your research scope.

If you haven’t yet narrowed your research focus down to a specific, answerable question, do that before you move forward with finding sources. Once you have a clear, specific thesis for your work, write a list of keywords related to that thesis you can use to streamline your source-gathering process. 

Find relevant literature

Using the keywords you listed, search for relevant sources through your university library and/or databases like Google Scholar, JSTOR, EBSCO, and field-specific databases like Project Muse and EconLit. 

As you find potential sources, read their abstracts to determine whether they are within your research’s scope. By reading a quick preview of each source (and taking note of recurring authors, contributors, and citations) you can pare down your list to a collection of works that provide the data, insights, and additional content you need to conduct your research. 

Identify themes, patterns, and gaps within your body of sources

Read your pared-down body of sources. As you conduct your research, take note of the themes present in them and ask questions: 

Examine the research methods each author used in their work. If your sources involve studies or experiments, note whether the results were replicated and where, if at all, the studies’ results varied from each other. 

Write down your key insights and how each source you consult contributes to the existing pool of knowledge on its subject. Explore how the sources challenge and contradict each other and where they agree or expand upon each other. 

Create a literature review outline

Writing an outline is an important part of the writing process . Once you’ve read your sources and you understand their themes, patterns, and connections to each other, it’s time to organize your strategy for writing about how you’ve used them in your research by creating an outline. 

There are a few different ways you can organize your outline. You can organize it chronologically , listing and discussing the oldest sources you’ve consulted and working up to the latest pieces. You can also organize your sources according to their themes , creating a section for each shared theme you encountered and discussing it there. Another way to organize your sources in your outline is to group them according to the research methods used by their authors. 

The best way to organize your literature review often depends on your subject area. In the humanities, presenting your sources chronologically or according to their themes can effectively highlight how existing research on your subject has evolved, whereas in the hard sciences, organizing your sources according to their research methods can enable you to highlight why the current scholarly consensus (if there is one!) is what it is. 

Write your literature review

Once your outline is complete, it’s time to start writing. In nearly all cases, literature reviews are written in the third person. For example, you might discuss a scholarly article by stating “this paper argues . . .” or “in her work, the author elaborates on . . .” However, there are cases where first person is appropriate in a literature review, such as when you’re referencing your own research. For example, if you’re citing an earlier paper you’ve written or data collected from a study you conducted, you may use phrases like “I argue,” “I propose,” and “through my research, I found that . . .”

Remember to follow the style you’re using for your research paper, whether that’s MLA , APA , or Chicago Manual of Style format. Similarly, use the same objective academic tone you’ll use in your research paper. Don’t just list and describe the sources you’ve read; respond to them, interpret them, and critically evaluate them. Keep in mind that you don’t have to agree with every source you use—in fact, exploring where your findings diverge from a source’s findings can be a strong point in your literature review and your research as a whole.  

Don’t forget to write an annotated bibliography of all your sources. Failing to cite your sources correctly can get you in trouble for plagiarism , which can potentially result in having your work discredited or even being expelled from your university. 

Literature review examples

Reading others’ literature reviews, especially literature reviews for research in your academic field, can be a very helpful way for you to understand how they work and see what you need to include in yours. 

Read the literature reviews of the sources you read in your own research. Your university might also have a resources page of literature review examples you can read. University of West Florida is one university that publishes literature review examples online .

Get academic writing just right

Academic writing is a lot different from other types of writing. While you want to strive for spot-on grammar and clear wording in everything you write, these factors are especially important in academic writing. There, you’re establishing yourself as a credible source on the topic you’ve covered—making polished, coherent writing essential. 

That’s also why it’s so important to strike the right tone in your academic writing—and it’s a tone you don’t find in many other kinds of work. Grammarly does more than catch your grammar mistakes and unclear writing; it detects your tone and offers valuable suggestions you can use to polish your writing into its final, submission-ready version. 

literature review and methods



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Effectiveness of prevention interventions using social marketing methods on behavioural change in the general population: a systematic review of the literature.

literature review and methods

1. Introduction

2.1. search strategy, 2.2. eligibility criteria.

2.3. Study Selection

2.4. data extraction, 2.5. assessment of methodological quality and risk of bias, 3.1. results of randomized trials, 3.2. results of systematic reviews, 3.3. methodological quality of systematic reviews, 4. discussion, 4.1. quality of the studies, 4.2. study limitations, 5. conclusions, supplementary materials, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

Share and Cite

Roger, A.; Dourgoudian, M.; Mergey, V.; Laplanche, D.; Ecarnot, F.; Sanchez, S. Effectiveness of Prevention Interventions Using Social Marketing Methods on Behavioural Change in the General Population: A Systematic Review of the Literature. Int. J. Environ. Res. Public Health 2023 , 20 , 4576. https://doi.org/10.3390/ijerph20054576

Roger A, Dourgoudian M, Mergey V, Laplanche D, Ecarnot F, Sanchez S. Effectiveness of Prevention Interventions Using Social Marketing Methods on Behavioural Change in the General Population: A Systematic Review of the Literature. International Journal of Environmental Research and Public Health . 2023; 20(5):4576. https://doi.org/10.3390/ijerph20054576

Roger, Aude, Mikael Dourgoudian, Virginie Mergey, David Laplanche, Fiona Ecarnot, and Stéphane Sanchez. 2023. "Effectiveness of Prevention Interventions Using Social Marketing Methods on Behavioural Change in the General Population: A Systematic Review of the Literature" International Journal of Environmental Research and Public Health 20, no. 5: 4576. https://doi.org/10.3390/ijerph20054576

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Russell R, Chung M, Balk EM, et al. Issues and Challenges in Conducting Systematic Reviews to Support Development of Nutrient Reference Values: Workshop Summary: Nutrition Research Series, Vol. 2. Rockville (MD): Agency for Healthcare Research and Quality (US); 2009 Mar. (Technical Reviews, No. 17.2.)

Cover of Issues and Challenges in Conducting Systematic Reviews to Support Development of Nutrient Reference Values: Workshop Summary

Issues and Challenges in Conducting Systematic Reviews to Support Development of Nutrient Reference Values: Workshop Summary: Nutrition Research Series, Vol. 2.

2 systematic review methods.

A systematic review is a protocol driven comprehensive review and synthesis of data focusing on a topic or on related key questions. It is typically performed by experienced methodologists with the input of domain experts.

The first step to conduct a systematic review is to formulate specific key questions. For situations that involve addressing more than a single, simple question, it is often useful to construct an analytic framework (evidence model) depicting the key questions being addressed to help appreciate their relationships. Furthermore, when many questions are being addressed, it may be beneficial to construct an “evidence map”, an exploratory exercise that informs on the amount of evidence potentially relevant to different questions. This information can aid in more detailed planning to allocate resources and ensure a timely completion of the project. Additional essential steps include developing a protocol, refining the questions of interest, conducting a literature search for evidence, selecting studies that meet the inclusion criteria, appraising the studies critically, and synthesizing and interpreting the results.

These steps are briefly described in this section. As mentioned above, systematic reviews should be carried out as a collaborative activity by individuals knowledgeable in the evidence-based methods and those with expertise in the questions of interest. As systematic reviews are increasingly being published on nutrition related topics, the term systematic review has been subjected to various modifications to include evidence-based review, systematic evidence-based review , and evidence-based systematic review . In this report, we use the term systematic review, which is the longstanding common usage in medicine and other disciplines.

Key Question Formulation

Overarching questions such as “What should be the upper intake level for vitamin A?” cannot be answered directly from primary data in the literature although the answer may be the ultimate goal of the exercise. The question must be dissected into smaller and more specific questions that individual studies can address. Multiple systematic reviews will then address these individual questions and the results will be synthesized according to a predefined framework. Thus, a vital step in performing a systematic review is formulating clearly stated research questions that would be amenable to literature review. “Key questions” are analogous to the hypotheses of primary research studies; they should be focused and explicitly stated because they define the scope of research the systematic review will address. Key questions are commonly formulated according to the “PICO” method, which defines the Population, the Intervention (or exposure in the case of observation studies), the appropriate Control or Comparator, and the Outcomes of interest. 16 Describing the inclusion criteria for each of the PICO elements clearly provides the investigators the opportunity to understand the specific questions being asked - and equally important, what questions are not being asked - in the systematic review. This step ensures reproducibility and transparency, and it guides the determination of study eligibility, data extraction, analysis, and interpretation of results. The reviewers must also decide which study designs are acceptable to answer specific questions. The choice about the types of evidence to be included is often a balance between what evidence is needed for conclusive answers to the review questions and the limitations of published studies. While randomized controlled trials may be ideal, these studies are often not practical or feasible, and other sources of evidence may need to be evaluated.

Analytic Framework

Figure 1. An example of a generic analytic framework used by the U.S. Preventive Services Task Force (USPSTF). Each number represents a specific link or answerable research question. A generic analytic framework for nutrient reference (more...)

Specifically, the analytic framework depicts the chain of logic that evidence must support to link the intervention or exposure to improved health outcomes. This process helps guide the development of key questions. The framework can also provide a basis for interpreting and contextualizing relevant studies, and establishing which links in the chain of logic are answered, inconclusive or not yet addressed.

Evidence Mapping to Inform the State of Evidence in a Particular Topic

Evidence mapping is a method to facilitate exploring new ideas and hypotheses. It can be used to direct limited resources to potentially more fruitful areas for systematic review as well as to complement comprehensive systematic reviews on specific key questions. It aims to provide investigators with information about the type and amount of research available, the characteristics of that research, and the topics where a sufficient amount of evidence has accumulated for synthesis.

Individual systematic reviews are labor intensive activities and might require the evaluation of hundreds of articles before identifying a handful of studies meeting the predetermined eligibility criteria. An evidence map to provide a “bird's eye” view requires only a fraction of the resources needed to produce a full systematic review, allowing users to appreciate the depth, breadth, and characteristics of research in a particular area before investing valuable resources in a full systematic review. Evidence mapping is a cost-effective method to inform users of the current state of research findings that could be used to generate hypotheses, inform ongoing research, and identify research gaps.

Critical Appraisal

The quality of an individual study has been defined as the “confidence that the trial (study) design, conduct, and analysis has minimized or avoided biases in its treatment (exposure) comparison.” 18 Quality assessment may suggest the extent to which a study's design and methodology prevented systematic error, and may explain differences in the results among systematic reviews. However, implementing and interpreting the results of quality assessment is not straightforward. Numerous approaches have been proposed to assess the quality of studies and apply these assessments to systematic reviews. Until recently, checklists and quality scales, generally comprised of several to several dozen factors believed to be associated with study quality, were commonly used.

Among the more common quality indicators for intervention trials are adequate concealment of random allocation, accurate reporting of withdrawals, degree of reporting accuracy, appropriateness of statistical analysis, and blinding in the assessment of outcomes. In theory, studies in which these measures are poorly achieved are more likely to result in biased outcomes. For example, compared to double-blinded studies, non-blinded studies may exaggerate the benefit of treatment (e.g. a larger odds ratio, or treatment effect). Of those criteria assessed, only lack of concealment of randomization and double blinding, with limited empirical evidence, have been shown to be related to exaggerated estimates of treatment effects. 19 However, other studies evaluating the importance of these quality measures have differed regarding the extent to which they were related to effect sizes. 20 – 22 Furthermore, individual quality measures may not be consistently associated with the magnitude of treatment effect across studies and medical areas. 23 As a result, methods that arbitrarily weight these measures to establish quality scores for studies are no longer deemed appropriate.

Approaches to assessing the quality of observational studies have been proposed; 24, 25 however, there are no empirical data validating any of these methods. The assessment of study quality is limited by the need to rely on author-supplied information and an understanding that there is no true reference standard for quality. 26 Critical appraisal of individual studies should be performed as part of a systematic review, but the results should be interpreted cautiously. The primary value may be to explore possible reasons for differences in results among studies. No specific instrument has been proposed to assess the quality of nutrition studies for the purpose of systematic review, although several factors (e.g., methods to assess dietary intake, quality of the statistical models used, independent replication of results from two or more laboratories) have been identified as important to consider based on the theoretical assumption that failure to adhere to the item proposed could lead to biased results.

Evidence Synthesis

A systematic review often identifies several studies addressing the same question. The results of these studies need to be synthesized and interpreted. Synthesis of the findings of different studies can be done qualitatively or quantitatively. It is not necessary for a systematic review to include quantitative analyses of individual study findings; however, when possible, quantitative analyses should be preferred over qualitative-only synthesis. Because quantitative synthesis has strengths and limitations, we briefly describe it below. An authoritative discussion on meta-analysis can be found in the Cochrane Handbook. 27

The quantitative synthesis of results obtained from different studies is termed meta-analysis. 28 By aggregating information from different studies, meta-analysis can increase statistical power and provide answers that no single study can give (i.e., detect modest associations, or conversely, exclude the presence of clinically important effects). For example, a meta-analysis of 19 clinical trials found a statistically significant increased overall mortality in participants who received “high doses” of vitamin E; 29 levels that had previously been considered as well below the upper limit, a finding that was not statistically significant in most of the individual studies. Of equal importance, meta-analysis quantifies between-study heterogeneity (between-study dissimilarity), and provides tools (e.g., meta-regression) to explain it. 30 Finally, meta-analysis facilitates the evaluation of systematic errors and biases, and their effect on any given topic.

Meta-analysis has sometimes been criticized as an inappropriate exercise of combining apples and oranges. Deciding when a meta-analysis is appropriate can be a challenge as there are numerous sources of heterogeneity that one needs to consider. If the designs, quality, and results of the studies are deemed to be so heterogeneous, then statistically combining them can yield misleading conclusions. In such cases where meta-analyses are deemed inappropriate, the data should be organized and presented in an analytic framework, and in summary evidence tables. This approach will help clarify the similarities and differences among studies that appear to address similar research question (qualitative synthesis).

Potential Challenges in Applying Evidence-based Methods to Support the Setting of Nutrient Reference Values

While the basic methodologies employed in systematic reviews of medical topics can be adapted to nutrition topics, there are also challenges and unique problems when incorporating the process into approaches to establish nutrient reference values. Many of these potential issues are unique to individual nutrients. Taking these factors into account while formulating the systematic review questions will minimize the risk of generating uninformative or wrong answers. The relative importance of each issue is nutrient specific. This section serves to provide a general discussion of potential issues to consider.

Many nutrients naturally occur in multiple bioactive forms. It is important to determine whether generally accepted nutrient conversion factors are valid in cases of marginal or excess intakes. The background or habitual diet of the study subjects is a critical factor that must be accounted for when extracting data from individual study reports. Response to deletion or supplementation of a nutrient will differ on the basis of this factor. It is important to document the nutrient status of the subjects prior to intervention, the status of body stores, and the potential bioavailability of those stores. It is also important to document body weight changes. Weight loss can result in hormonal changes and subsequent release of certain nutrients (e.g. iron status) not normally available. 30, 31 Alternatively, weight gain can create nutrient reservoirs (e.g. fat soluble vitamins) that are unavailable in times of nutrient, but not energy, need. 30, 32, 33

Some factors are particularly important and should be taken into account when data from multiple populations are examined. These include differences in nutrient bioequivalency that depend on the type of natural or fortified foods available to the general population (e.g. heme and nonheme iron); differences in food processing techniques (e.g. lye treated corn and niacin); and differences in whether the major source of the nutrient is limited to naturally occurring forms or whether a synthetic form is commonly added to in the food supply (e.g. folate and enriched grains). The increasingly common practice of supplementing foods with nutrients may also need to be accounted for (e.g. nutrient-fortified soft drinks, calcium-fortified orange juice). Additional factors that are important in cross-cultural comparisons include nutrient bioavailability as altered by coingestion of other foods, supplemental nutrients or drugs, and non-food sources of a nutrient (e.g. sun exposure and vitamin D, gut microflora and vitamin K).

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    A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic. There are five key steps to writing a literature review:

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    This type of review requires attention to non-biased analysis of the literature by use of a defined scientific method, such as described within the PRISMA Statement. 1 Systematic reviews require minimization of error both in conduct of the review and within the literature included within the review.

  9. Literature Review and Method Section Final

    Alexis Herrera Psych 2305: Introduction to Methods in Psychology Diana Bravo 9 March 2022. Abstract Postpartum depression is a common and widespread issue among many mothers. There are several factors that may contribute to the development of such symptoms.

  10. Literature Review and Methods.pdf

    Soc 310 Literature Review and Methods After going through the education system in the United States and seeing the different outcomes it can produce, it made me curious on how different types of education impact students. The United States has various different types of school systems but all falling under the umbrella of private and public schools. There has always been lots of controversy ...

  11. PDF Literature Reviews: Methods and Applications

    Literature Review). Narrative reviews may also outline methods or research design that is used for a particular study topic (Methodological Literature Review), or provide a historical evalu-ation of the development of theory or concepts for a topic (Historical Literature Review). Narrative reviews may be con-

  12. Application of MADM methods in Industry 4.0: A literature review

    The literature review investigates multi attribute decision making methods in Industry 4.0. ... PROMETHEE methods were the most frequently encountered ranking methods in our review, with 17 articles, as they allow experts evaluating alternatives to probably not have full and complete knowledge of all criteria, but also to clearly articulate the ...

  13. Literature Review

    Research Methods and Design Definition Literature Review A literature review is a discussion of the literature (aka. the "research" or "scholarship") surrounding a certain topic. A good literature review doesn't simply summarize the existing material, but provides thoughtful synthesis and analysis.

  14. PDF How to Write a Literature Review

    of a literature review are. The Purpose of a Literature Review A literature review demonstrates your ability to research; it also showcases your expertise on your chosen topic. By including a literature review in your project or thesis, you are also providing your reader with the most prevalent theories and studies on your topic, evaluations ...

  15. Research Methods: Literature Reviews

    Definition A literature review involves researching, reading, analyzing, evaluating, and summarizing scholarly literature (typically journals and articles) about a specific topic. The results of a literature review may be an entire report or article OR may be part of a article, thesis, dissertation, or grant proposal.

  16. Types of Literature Review

    Systematic literature review can be divided into two categories: meta-analysis and meta-synthesis. When you conduct meta-analysis you take findings from several studies on the same subject and analyze these using standardized statistical procedures. In meta-analysis patterns and relationships are detected and conclusions are drawn.

  17. Literature review example analysis

    Chapter 1: Literature review of relevant research The overall goals of this chapter are to firstly establish the significance of the general field of study, and then identify a place where a new contribution could be made.

  18. Literature Review Research

    Literature Review is a comprehensive survey of the works published in a particular field of study or line of research, usually over a specific period of time, in the form of an in-depth, critical bibliographic essay or annotated list in which attention is drawn to the most significant works.

  19. Spontaneous remission of acute lymphoblastic leukemia: A series of nine

    Methods. We identified and analyzed nine patients with ALL and spontaneous remission. Review of literature reveals an additional nine previously reported cases with similar clinical course. Results. All of these patients, ranging in age from 2 to 12 years of age, presented with inciting signs and symptoms of viral or bacterial infection.

  20. Literature Review Methodology

    The first reason methodology is important in the literature review is that it is used to sort out points. This is very much needed to avoid jumbling up ideas without directives. With patterns of guides for writing, your research paper will be organized and durable for reading.

  21. Types of Reviews

    This site explores different review methodologies such as, systematic, scoping, realist, narrative, state of the art, meta-ethnography, critical, and integrative reviews. The LITR-EX site has a health professions education focus, but the advice and information is widely applicable. Types of Reviews

  22. (PDF) Literature Review as a Research Methodology: An overview and

    Methods of Literature review . Below are some various methods used in reviewing a paper as a research. methodology(T emplier and Paré, 2015). A variety of current literature review protocols are ...

  23. Literature Review: Conducting & Writing

    Literature Review: Conducting & Writing Sample Lit Reviews from Communication Arts Literature Review Sample 1 Literature Review Sample 2 Literature Review Sample 3 Have an exemplary literature review? Have you written a stellar literature review you care to share for teaching purposes?

  24. A systematic review of published literature on mosquito control action

    Methods. The systematic review was conducted following the PRISMA 2020 guidelines . A protocol was prepared and agreed upon by all authors. An appropriate literature search was conducted from March 2020 to July 2021 using two main public search engines, Google Scholar (GS) and PubMed Central (PMC).

  25. Systematic Review

    Published on June 15, 2022 by Shaun Turney . Revised on December 7, 2022. A systematic review is a type of review that uses repeatable methods to find, select, and synthesize all available evidence. It answers a clearly formulated research question and explicitly states the methods used to arrive at the answer.

  26. How to Write a Stellar Literature Review

    A literature review requires the same style as any other piece of academic writing. That means no contractions or colloquialisms, concise language, formal tone, and an objective perspective at all times. To distinguish between your analysis and prior scholarly work in the field, use the past tense when discussing the previous research conducted ...

  27. IJERPH

    Similarly, the communication methods used across all the interventions varied widely, although few, if any studies gave concrete details of the actual supports used to diffuse the messages. ... A review of the literature and research perspectives. L'Année Psychol. 2016, 116, 67-103. [Google Scholar] Witte, K.; Allen, M. A meta-analysis of ...

  28. Systematic Review Methods

    Systematic Review Methods - Issues and Challenges in Conducting ...