Conducting a Literature Review in Health Research: 5

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1. Frame review question quantitative studies, PICOS framework would be used for 2. Identify relevant work study selection, whereas if a review seeks to summarize Review Article 3. Assess study quality qualitative studies, then the appropriate tool would be 4. Summarize evidence SPIDER framework7. These two tools are described in Conducting a Literature Review in Health Research: 5. Interpret findings Box-1 and 2. These five steps are elaborated upon in Figure – 1. Basics of the Approach, Typology and Methodology Box-1: Elaboration and explanation of PICOS with an Figure-1: Steps of conducting a systematic review. example of a systematic review. Ahmed S1, Vaska M2, Turin TC1,3,4 Elaboration of PICOS: 1Department of Family Medicine, University of Calgary, Calgary, Alberta, Canada, 2Knowledge Resource Service, Alberta P: Population Health Services, Calgary, Alberta, Canada, 3Department of Community Health Sciences, University of Calgary, Calgary, I: Intervention Alberta, Canada, 4Department of Epidemiology & Research, National Heart Foundation Hospital & Research Institute, C: Comparison Dhaka, Bangladesh. O: Outcome S: Study Design Abstract Background: Literature reviews play a significant role in healthcare practice. There are different types of reviews available Example: Virtual Reality in Stroke Rehabilitation: A depending on the nature of the research question and the extent of reviewing that is conducted. In this article, we have Systematic Review of its Effectiveness for Upper Limb summarized the major types of literature reviews, their strength and weakness, and provide representative examples. Motor Recovery (PMID: 17517575).

Methods: We have examined the different types of common reviews that have been used in the health research literature. We P: Patients with post-stroke hemiplegia collected the information on these review types and have summarized them with providing corresponding examples. I: Immersive or non-immersive virtual reality C: Conventional therapy or no therapy Results: We have discussed the major types of reviews: literature review, critical review, scoping review, systematic review, O: Differences between groups meta-analysis, qualitative systematic review, realist review, and review of reviews. We have mentioned the usability, S: Experimental studies including randomized controlled strengths and weaknesses, utilizing the Search, Appraisal, Synthesis, Analysis (SALSA) framework, and have provided trials (RCTs). corresponding examples for each of these types of reviews in different tables. Box-2: Elaboration and explanation of SPIDER with an Conclusion: This article is a summary of different types of reviews and their implication in practice. This paper is thus example of qualitative systematic intended for beginners who want to know about literature reviews. (JNHFB 2016; 5 : 44-51) review.

Elaboration of SPIDER: Introduction S: Sample Literature reviews are becoming more and more important to summarize the existing knowledge and identify the PI: Phenomenon of Interest and favoured in the evidencebased practice (EBP) of health potential gaps for future research4. However, a literature D: Design and social care1. Healthcare professionals require updated review can be undertaken for other reasons such as E: Evaluation information regarding research and development to inform generating and refining a research idea, creating awareness R: Research type their practice. However, with such large amounts of of the current state of knowledge in a subject area, determining Example: Smoke-free homes: what are the barriers, motiva- materials being published, it is impossible for anyone to how research fits into the wider context, etc. The bottom line tors and enablers? A qualitative systematic review and cover every single piece of information or evidence on any is that before beginning a review, researchers should be thematic synthesis (PMID: 26988351) given topic. A literature review thus gives audiences the clear about the purpose of doing a review as well as the S: Families, households and vulnerable populations opportunity to have summarized information on any topic expected outcome(s). The objective behind the initiation of PI: Barriers, motivators and enablers of smoke-free home without reading all of the evidence published in that specific the review directs the type of review that needs to be D: Any qualitative data collection method (interview, focus area. Although the culture of the review article began more chosen5. group etc.) than two centuries ago, it wasn’t until the 20th century that E: Critical Appraisal Skills Program (CASP) Qualitative an explicit method was devised to carry out review In this article we describe the elements that we need to Checklist research2. In addition, the emergence of EBP instigated consider when we envisage conducting a review. We then R: Qualitative more rigorous and quality controlled approaches of review summarize the major types of reviews that are widely used articles so that the synthesized summary results could be by the scientific community. We also discuss the objectives utilized with confidence3. that these reviews serve and summarize the strengths and Based on the type of the review, one or more of the For quality assessment, there are different types of tools weaknesses of each type. above-mentioned step(s) can be altered or removed. In available according to the source literature8. For example, Reasons for undertaking a literature review general, Frame review question, Summarize evidence and the Consolidated for Reporting Qualitative Research In general, the main goal of conducting a literature review is Planning a review Interpret findings depends on the author’s choice or journal (COREQ) or the Standards for Reporting Qualitative Corresponding Author Based on the type, a literature review can range from “just requirements. However, according to the nature of the Research (SRQR) is recognized for quality assessment of Tanvir C Turin MBBS MS PhD reviews, study identification and quality assessment 9, 10 Department of Family Medicine, narrative write-up” to “very organized”. A review is the qualitative studies while the Effective Public Health Room G012F, Health Sciences Center, usually structured according to the following steps6: techniques vary. For example, if a review aims to catalogue Practice Project (EPHPP) is an example of a quantitative 3330 Hospital Drive Northwest, Calgary, Alberta T2N 4N1, Canada.

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study quality assessment tool11. The Equator Network • Follows a formal process for apprais- (http://www.equator-network.org/reporting-guidelines/) provides ing literature and minimizing bias. a comprehensive list of reporting and quality assessment tools for different types of studies. • Follows a standard scientific protocol; this type of review is considered Major types of reviews original research. Review articles are of different types based on the purpose of the review and the research question to address12. In this Meta-analysis • This is a technique that is commonly brief article, we’ll cover 8 major types of literature reviews. used in systematic reviews to statisti- These are: literature review, critical review, scoping review, cally combine the results of quantita- systematic review, meta-analysis, qualitative systematic tive studies to provide a more precise review, realist review, and review of reviews. The subse- pooled effect of the results. quent paragraphs will briefly mention these different types of review articles. Major characteristics, methods of • Also gives the reader an understand- SALSA, strengths and weaknesses, and examples of each of ing of differences (heterogeneity) in the different types of reviews are given in Table 1-4. the results across thestudies.

Table-1: Major types of reviews in the health research. • Requires all the included studies to be sufficiently similar.

• Reviewer will also present informa- explanatory focus. • Realist reviews uncover the mecha- tion that will allow the reader to make nism(s) of how and why complex a value judgment about the article. interventions thrive or fail, in any Scoping review • Maps existing literature or evidence given particular setting. base on a particular topic. Review of • Refers to a review compiling evidence • Identify the nature and extent of reviews from multiple reviews into one acces- evidences available. sible and usable document.

• Also used to identify parameters and • Useful for any broad condition or gaps in a body of literature. problem where multiple and contra- Systematic • Use explicit method to identify dicting or competing interventions review reliable information as much as are present in the form of systematic possible regarding a research reviews. question.

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1. Literature review 5. Meta-analysis The term “literature review” is broad in scope and difficult A Meta-analysis is not actually a standalone type of review to isolate from other types of review articles. However, it is article, but is rather commonly used in conjunction with a general summary of published literature on any topic systematic review. A meta-analysis is basically a statistical without requiring a systematic search for literature, and a method of aggregating sufficiently similar articles to rigorous inclusion/exclusion procedure. A literature review compare the outcomes from different sources. Metaanalytic provides a good source of summarized knowledge, but due compilations are good resources for decision makers, as to the lack of methodological rigour, it can be biased by they reduce the time required to review scattered individual reflecting the author’s own point of view12. studies16.

2. Critical Review 6. Qualitative systematic review A critical review is not just a summary of the literature; Qualitative studies have gained considerable importance in rather, it demonstrates extensive research and quality current medical and social science literature. A qualitative evaluation. Authors of critical reviews do not need to systematic review is an approach used to integrate and mention every single element from the source literature, but compare the findings from qualitative literature on a specific 17 instead extract the most important ideas from the sources topic . cited13. Generally, the findings of critical reviews are typically hypotheses or models. 7. Realist review A realist review arose from the need to deal with complex 3. Scoping review interventions and heterogeneity of study design, study 18 A scoping review focuses on identifying the nature and settings, context, outcome measures etc . Systematic extent of literature available on any specific topic. It is reviews are ideal for simple and single interventions, similar to a systematic review with the exception that it however, in reality, healthcare professionals and policy provides a quality assessment of primary literature. This makers usually deal with multiple interventions in complex type of review unveils the scope of future research and may scenarios. Instead of a straightforward answer to a question, lead to conducting a systematic review on the topic to gain a realist review will provide a rich, detailed and practical more specific knowledge14. understanding of complex social interventions.

4. Systematic review 8. Review of reviews A systematic review follows an arduous protocol (which A review of reviews generally compiles evidence from may or may not be peer-reviewed), rendering it replicable multiple reviews into one single document. In many by any other researcher15. Therefore, systematic reviews are disciplines, decision makers are overwhelmed with numer- considered to be key elements of evidence-based healthcare ous systematic reviews of varying quality and scope. This information and are thus regarded as the strongest form of situation has triggered the need for a systematic review of medical evidence. The methodology of a systematic review reviews where the quality of every review is assessed and is driven by a framework called PICOS (described in Box the results are compared. Therefore, the decision maker is 1). PICOS tools are designed to capture quantitative studies better able to understand the interventions identified in and, with the advent of qualitative research in healthcare, a different reviews19. different genre of review has been developed, namely the qualitative systematic review.

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Conducting a Literature Review in Health Research: Basics of the Approach Ahmed S et al.

1. Frame review question quantitative studies, PICOS framework would be used for 2. Identify relevant work study selection, whereas if a review seeks to summarize 3. Assess study quality qualitative studies, then the appropriate tool would be 4. Summarize evidence SPIDER framework7. These two tools are described in 5. Interpret findings Box-1 and 2. These five steps are elaborated upon in Figure – 1. Box-1: Elaboration and explanation of PICOS with Figure-1: Steps of conducting a systematic review. an example of a systematic review.

Frame review question: Elaboration of PICOS: P: Population Specify the problem to be addressed by I: Intervention the review. C: Comparison Keep this statement as clear, O: Outcome unambiguous and structured as possible. S: Study Design

Example: Virtual Reality in Stroke Rehabilitation: A Systematic Review of its Effectiveness for Upper Limb Identify relevant work : Motor Recovery (PMID: 17517575). Sources of literature, search terms and P: Patients with post-stroke hemiplegia keywords etc. I: Immersive or non-immersive virtual reality Study selection method, C: Conventional therapy or no therapy Inclusion/exclusion criteria O: Differences between groups S: Experimental studies including randomized controlled trials (RCTs). Assess study quality : Box-2: Elaboration and explanation of SPIDER with Select a quality assessment method based an example of qualitative systematic review. on the type of source literature. Elaboration of SPIDER: S: Sample Introduction PI: Phenomenon of Interest Literature reviews are becoming more and more important to summarize the existing knowledge and identify the Summarize evidence : D: Design and favoured in the evidencebased practice (EBP) of health potential gaps for future research4. However, a literature E: Evaluation and social care1. Healthcare professionals require updated review can be undertaken for other reasons such as Summarized information can be R: Research type information regarding research and development to inform generating and refining a research idea, creating awareness presented in tabular format, meta- their practice. However, with such large amounts of of the current state of knowledge in a subject area, determining analysis etc. Example: Smoke-free homes: what are the barriers, motiva- materials being published, it is impossible for anyone to how research fits into the wider context, etc. The bottom line tors and enablers? A qualitative systematic review and cover every single piece of information or evidence on any is that before beginning a review, researchers should be thematic synthesis (PMID: 26988351) given topic. A literature review thus gives audiences the clear about the purpose of doing a review as well as the opportunity to have summarized information on any topic expected outcome(s). The objective behind the initiation of Interpret findings : S: Families, households and vulnerable populations without reading all of the evidence published in that specific the review directs the type of review that needs to be PI: Barriers, motivators and enablers of smoke-free home May cover all or multiples of these: area. Although the culture of the review article began more chosen5. D: Any qualitative data collection method (interview, focus heterogeneity of the studies, strengths than two centuries ago, it wasn’t until the 20th century that group etc.) and weaknesses, study quality, future an explicit method was devised to carry out review In this article we describe the elements that we need to E: Critical Appraisal Skills Program (CASP) Qualitative research2. In addition, the emergence of EBP instigated consider when we envisage conducting a review. We then recommendations, etc. Checklist more rigorous and quality controlled approaches of review summarize the major types of reviews that are widely used R: Qualitative articles so that the synthesized summary results could be by the scientific community. We also discuss the objectives utilized with confidence3. that these reviews serve and summarize the strengths and Based on the type of the review, one or more of the For quality assessment, there are different types of tools 8 weaknesses of each type. above-mentioned step(s) can be altered or removed. In available according to the source literature . For example, Reasons for undertaking a literature review general, Frame review question, Summarize evidence and the Consolidated for Reporting Qualitative Research In general, the main goal of conducting a literature review is Planning a review Interpret findings depends on the author’s choice or journal (COREQ) or the Standards for Reporting Qualitative Based on the type, a literature review can range from “just requirements. However, according to the nature of the Research (SRQR) is recognized for quality assessment of 9, 10 narrative write-up” to “veryorganized”. A review is usually reviews, study identification and quality assessment the qualitative studies while the Effective Public Health structured according to the following steps6: techniques vary. For example, if a review aims to catalogue Practice Project (EPHPP) is an example of a quantitative

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Table-1: Major types of reviews in the health research. • Requires all the included studies to be sufficiently similar.

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1. Frame review question quantitative studies, PICOS framework would be used for 2. Identify relevant work study selection, whereas if a review seeks to summarize 3. Assess study quality qualitative studies, then the appropriate tool would be 4. Summarize evidence SPIDER framework7. These two tools are described in 5. Interpret findings Box-1 and 2. These five steps are elaborated upon in Figure – 1. Box-1: Elaboration and explanation of PICOS with an Figure-1: Steps of conducting a systematic review. example of a systematic review.

Elaboration of PICOS: P: Population I: Intervention C: Comparison O: Outcome S: Study Design

Example: Virtual Reality in Stroke Rehabilitation: A Systematic Review of its Effectiveness for Upper Limb Motor Recovery (PMID: 17517575).

P: Patients with post-stroke hemiplegia I: Immersive or non-immersive virtual reality C: Conventional therapy or no therapy O: Differences between groups S: Experimental studies including randomized controlled trials (RCTs).

Box-2: Elaboration and explanation of SPIDER with an example of qualitative systematic review.

Elaboration of SPIDER: Introduction S: Sample Literature reviews are becoming more and more important to summarize the existing knowledge and identify the PI: Phenomenon of Interest and favoured in the evidencebased practice (EBP) of health potential gaps for future research4. However, a literature D: Design and social care1. Healthcare professionals require updated review can be undertaken for other reasons such as E: Evaluation information regarding research and development to inform generating and refining a research idea, creating awareness R: Research type their practice. However, with such large amounts of of the current state of knowledge in a subject area, determining Example: Smoke-free homes: what are the barriers, motiva- materials being published, it is impossible for anyone to how research fits into the wider context, etc. The bottom line tors and enablers? A qualitative systematic review and cover every single piece of information or evidence on any is that before beginning a review, researchers should be thematic synthesis (PMID: 26988351) given topic. A literature review thus gives audiences the clear about the purpose of doing a review as well as the S: Families, households and vulnerable populations opportunity to have summarized information on any topic expected outcome(s). The objective behind the initiation of PI: Barriers, motivators and enablers of smoke-free home without reading all of the evidence published in that specific the review directs the type of review that needs to be D: Any qualitative data collection method (interview, focus area. Although the culture of the review article began more chosen5. group etc.) than two centuries ago, it wasn’t until the 20th century that E: Critical Appraisal Skills Program (CASP) Qualitative an explicit method was devised to carry out review In this article we describe the elements that we need to Checklist research2. In addition, the emergence of EBP instigated consider when we envisage conducting a review. We then R: Qualitative more rigorous and quality controlled approaches of review summarize the major types of reviews that are widely used articles so that the synthesized summary results could be by the scientific community. We also discuss the objectives utilized with confidence3. that these reviews serve and summarize the strengths and Based on the type of the review, one or more of the For quality assessment, there are different types of tools weaknesses of each type. above-mentioned step(s) can be altered or removed. In available according to the source literature8. For example, Reasons for undertaking a literature review general, Frame review question, Summarize evidence and the Consolidated for Reporting Qualitative Research In general, the main goal of conducting a literature review is Planning a review Interpret findings depends on the author’s choice or journal (COREQ) or the Standards for Reporting Qualitative Based on the type, a literature review can range from “just requirements. However, according to the nature of the Research (SRQR) is recognized for quality assessment of narrative write-up” to “veryorganized”. A review is usually reviews, study identification and quality assessment the qualitative studies9, 10 while the Effective Public Health structured according to the following steps6: techniques vary. For example, if a review aims to catalogue Practice Project (EPHPP) is an example of a quantitative

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JNHFB Jul 2016 Ahmed S et al. study quality assessment tool11. The Equator Network • Follows a formal process for apprais- (http://www.equator-network.org/reporting-guidelines/) provides ing literature and minimizing bias. a comprehensive list of reporting and quality assessment tools for different types of studies. • Follows a standard scientific protocol; this type of review is considered Major types of reviews original research. Review articles are of different types based on the purpose of the review and the research question to address12. In this Meta-analysis • This is a technique that is commonly brief article, we’ll cover 8 major types of literature reviews. used in systematic reviews to statisti- These are: literature review, critical review, scoping review, cally combine the results of quantita- systematic review, meta-analysis, qualitative systematic tive studies to provide a more precise review, realist review, and review of reviews. The subse- pooled effect of the results. quent paragraphs will briefly mention these different types of review articles. Major characteristics, methods of • Also gives the reader an understand- SALSA, strengths and weaknesses, and examples of each of ing of differences (heterogeneity) in the different types of reviews are given in Table 1-4. the results across thestudies.

Table-1: Major types of reviews in the health research. • Requires all the included studies to be sufficiently similar.

Type Description • A comprehensive meta-analysis will give the reader an idea if new studies Literature review • Provides examination of current or are needed to further investigate an recent literature to answer a specific issue. research question or to describe a broad topic. Qualitative • Looks for ‘themes’ or ‘constructs’ Systematic that lie in or across individual • Involves some processes of inclusion Review systematic review qualitative studies. criteria for the literature but a formal systematic literature search is not • Interpretative in broadening under- mandatory. standing of a particular phenomenon. • Involves synthesizing the selected literature in a textual, tabular or Realist review • A theory-driven, qualitative and graphic format. mixed-method approach to a systematic review as an alternative to (or to Critical review • Requires that the reviewer understand extend and supplement) conventional the material, and know how to Cochrane-style reviews. analyze and evaluate that material A relatively new approach to synthe- using appropriate criteria (strengths, • size research that seeks an weaknesses, and validity). explanatory focus. • Reviewer will also present informa- • Realist reviews uncover the mecha- tion that will allow the reader to make nism(s) of how and why complex a value judgment about the article. interventions thrive or fail, in any Scoping review • Maps existing literature or evidence given particular setting. base on a particular topic. Review of • Refers to a review compiling evidence • Identify the nature and extent of reviews from multiple reviews into one acces- evidences available. sible and usable document.

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1. Frame review question quantitative studies, PICOS framework would be used for 2. Identify relevant work study selection, whereas if a review seeks to summarize 3. Assess study quality qualitative studies, then the appropriate tool would be 4. Summarize evidence SPIDER framework7. These two tools are described in 5. Interpret findings Box-1 and 2. These five steps are elaborated upon in Figure – 1. Box-1: Elaboration and explanation of PICOS with an Figure-1: Steps of conducting a systematic review. example of a systematic review.

Elaboration of PICOS: P: Population I: Intervention C: Comparison O: Outcome S: Study Design

Example: Virtual Reality in Stroke Rehabilitation: A Systematic Review of its Effectiveness for Upper Limb Motor Recovery (PMID: 17517575).

Box-2: Elaboration and explanation of SPIDER with an example of qualitative systematic review.

Elaboration of SPIDER: Introduction S: Sample Literature reviews are becoming more and more important to summarize the existing knowledge and identify the PI: Phenomenon of Interest and favoured in the evidencebased practice (EBP) of health potential gaps for future research4. However, a literature D: Design and social care1. Healthcare professionals require updated review can be undertaken for other reasons such as E: Evaluation information regarding research and development to inform generating and refining a research idea, creating awareness R: Research type their practice. However, with such large amounts of of the current state of knowledge in a subject area, determining Example: Smoke-free homes: what are the barriers, motiva- materials being published, it is impossible for anyone to how research fits into the wider context, etc. The bottom line tors and enablers? A qualitative systematic review and cover every single piece of information or evidence on any is that before beginning a review, researchers should be thematic synthesis (PMID: 26988351) given topic. A literature review thus gives audiences the clear about the purpose of doing a review as well as the S: Families, households and vulnerable populations opportunity to have summarized information on any topic expected outcome(s). The objective behind the initiation of PI: Barriers, motivators and enablers of smoke-free home without reading all of the evidence published in that specific the review directs the type of review that needs to be D: Any qualitative data collection method (interview, focus area. Although the culture of the review article began more chosen5. group etc.) than two centuries ago, it wasn’t until the 20th century that E: Critical Appraisal Skills Program (CASP) Qualitative an explicit method was devised to carry out review In this article we describe the elements that we need to Checklist research2. In addition, the emergence of EBP instigated consider when we envisage conducting a review. We then R: Qualitative more rigorous and quality controlled approaches of review summarize the major types of reviews that are widely used articles so that the synthesized summary results could be by the scientific community. We also discuss the objectives utilized with confidence3. that these reviews serve and summarize the strengths and Based on the type of the review, one or more of the For quality assessment, there are different types of tools weaknesses of each type. above-mentioned step(s) can be altered or removed. In available according to the source literature8. For example, Reasons for undertaking a literature review general, Frame review question, Summarize evidence and the Consolidated for Reporting Qualitative Research In general, the main goal of conducting a literature review is Planning a review Interpret findings depends on the author’s choice or journal (COREQ) or the Standards for Reporting Qualitative Based on the type, a literature review can range from “just requirements. However, according to the nature of the Research (SRQR) is recognized for quality assessment of narrative write-up” to “veryorganized”. A review is usually reviews, study identification and quality assessment the qualitative studies9, 10 while the Effective Public Health structured according to the following steps6: techniques vary. For example, if a review aims to catalogue Practice Project (EPHPP) is an example of a quantitative

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Conducting a Literature Review in Health Research: Basics of the Approach Ahmed S et al.

11 study quality assessment tool . The Equator Network • Follows a formal process for apprais- Table – 2: Major types of reviews described using the Search, Appraisal, Synthesis and Analysis (SALSA) framework (http://www.equator-network.org/reporting-guidelines/) provides ing literature and minimizing bias. Type Search Appraisal Synthesis Analysis a comprehensive list of reporting and quality assessment tools for different types of studies. • Follows a standard scientific proto- Literature May or may not May or may not include Typically narrative Analysis may be col; this type of review is considered review include quality assessment chronological, Major types of reviews original research. comprehensive conceptual, Review articles are of different types based on the purpose searching thematic, etc. of the review and the research question to address12. In this Meta-analysis • This is a technique that is commonly Critical Seeks to identify No formal quality Typically narrative Seeks to identify brief article, we’ll cover 8 major types of literature reviews. used in systematic reviews to statisti- review most significant assessment conceptual These are: literature review, critical review, scoping review, cally combine the results of quantita- items in the field contribution to systematic review, meta-analysis, qualitative systematic tive studies to provide a more precise embody existing review, realist review, and review of reviews. The subse- pooled effect of the results. conjecture or quent paragraphs will briefly mention these different types derive new of review articles. Major characteristics, methods of • Also gives the reader an understand- proposition SALSA, strengths and weaknesses, and examples of each of ing of differences (heterogeneity) in Scoping Completeness of No formal quality Typically tabular with Characterizes the different types of reviews are given in Table 1-4. the results across thestudies. review searching determined assessment some narrative quantity and by time/scope commentary quality of Table-1: Major types of reviews in the health research. • Requires all the included studies to be constraints literature, perhaps sufficiently similar. by study design and other key Type Description • A comprehensive meta-analysis will features deemed important by the give the reader an idea if new studies researcher Literature review • Provides examination of current or are needed to further investigate an recent literature to answer a specific issue. Systematic Exhaustive and Quality assessment is Typically narrative with What is known research question or to describe a review comprehensive common and may tabular accompaniment Recommendations broad topic. Qualitative • Looks for ‘themes’ or ‘constructs’ searching determine for practice that lie in or across individual inclusion/exclusion What remains criteria • Involves some processes of inclusion systematic review qualitative studies. unknown; criteria for the literature but a formal uncertainty systematic literature search is not around findings, • Interpretative in broadening under- recommendations mandatory. standing of a particular phenomenon. for future research • Involves synthesizing the selected Meta- Comprehensive Quality assessment and Graphical and tabular Statistical analysis literature in a textual, tabular or Realist review • A theory-driven, qualitative and analysis searching sensitivity analysis with narrative of measures of graphic format. mixed-method approach to a systematic review as an alternative to (or to commentary effect Critical Review • Requires that the reviewer understand extend and supplement) conventional Qualitative May employ Quality assessment Qualitative, narrative Thematic the material, and know how to Cochrane-style reviews. systematic selective or purposive typically used to mediate synthesis and analyze and evaluate that material review sampling messages not for analysis using appropriate criteria (strengths, • A relatively new approach to synthe- inclusion/exclusion weaknesses, and validity). size research that seeks an Realist Formal systematic Assessment of relevance Typically tabular with Identify the • Reviewer will also present informa- review search and rigor some narrative explanatory focus. • Realist reviews uncover the mecha- commentary works, how, for tion that will allow the reader to make nism(s) of how and why complex whom, in what a value judgment about the article. interventions thrive or fail, in any circumstances and given particular setting. Scoping review • Maps existing literature or evidence for any base on a particular topic. intervention Review of • Refers to a review compiling evidence • Identify the nature and extent of reviews from multiple reviews into one acces- Review of Identification of Quality assessment of Graphical and tabular What is known; evidences available. sible and usable document. reviews component reviews, studies within component with narrative recommendations but not primary reviews commentary for practice studies What remains • Also used to identify parameters and • Useful for any broad condition or gaps in a body of literature. unknown; problem where multiple and contra- recommendations Systematic • Use explicit method to identify dicting or competing interventions for future research review reliable information as much as are present in the form of systematic possible regarding a research reviews. NB. The details of The Search, Appraisal, Synthesis and Analysis (SALSA) framework presented with permission from John Wiley and Sons from the question. following reference: Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal. 2009;26(2):91-108.

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1. Frame review question quantitative studies, PICOS framework would be used for 2. Identify relevant work study selection, whereas if a review seeks to summarize 3. Assess study quality qualitative studies, then the appropriate tool would be 4. Summarize evidence SPIDER framework7. These two tools are described in 5. Interpret findings Box-1 and 2. These five steps are elaborated upon in Figure – 1. Box-1: Elaboration and explanation of PICOS with an Figure-1: Steps of conducting a systematic review. example of a systematic review.

Elaboration of PICOS: P: Population I: Intervention C: Comparison O: Outcome S: Study Design

Example: Virtual Reality in Stroke Rehabilitation: A Systematic Review of its Effectiveness for Upper Limb Motor Recovery (PMID: 17517575).

Box-2: Elaboration and explanation of SPIDER with an example of qualitative systematic review.

Elaboration of SPIDER: Introduction S: Sample Literature reviews are becoming more and more important to summarize the existing knowledge and identify the PI: Phenomenon of Interest and favoured in the evidencebased practice (EBP) of health potential gaps for future research4. However, a literature D: Design and social care1. Healthcare professionals require updated review can be undertaken for other reasons such as E: Evaluation information regarding research and development to inform generating and refining a research idea, creating awareness R: Research type their practice. However, with such large amounts of of the current state of knowledge in a subject area, determining Example: Smoke-free homes: what are the barriers, motiva- materials being published, it is impossible for anyone to how research fits into the wider context, etc. The bottom line tors and enablers? A qualitative systematic review and cover every single piece of information or evidence on any is that before beginning a review, researchers should be thematic synthesis (PMID: 26988351) given topic. A literature review thus gives audiences the clear about the purpose of doing a review as well as the S: Families, households and vulnerable populations opportunity to have summarized information on any topic expected outcome(s). The objective behind the initiation of PI: Barriers, motivators and enablers of smoke-free home without reading all of the evidence published in that specific the review directs the type of review that needs to be D: Any qualitative data collection method (interview, focus area. Although the culture of the review article began more chosen5. group etc.) than two centuries ago, it wasn’t until the 20th century that E: Critical Appraisal Skills Program (CASP) Qualitative an explicit method was devised to carry out review In this article we describe the elements that we need to Checklist research2. In addition, the emergence of EBP instigated consider when we envisage conducting a review. We then R: Qualitative more rigorous and quality controlled approaches of review summarize the major types of reviews that are widely used articles so that the synthesized summary results could be by the scientific community. We also discuss the objectives utilized with confidence3. that these reviews serve and summarize the strengths and Based on the type of the review, one or more of the For quality assessment, there are different types of tools weaknesses of each type. above-mentioned step(s) can be altered or removed. In available according to the source literature8. For example, Reasons for undertaking a literature review general, Frame review question, Summarize evidence and the Consolidated for Reporting Qualitative Research In general, the main goal of conducting a literature review is Planning a review Interpret findings depends on the author’s choice or journal (COREQ) or the Standards for Reporting Qualitative Based on the type, a literature review can range from “just requirements. However, according to the nature of the Research (SRQR) is recognized for quality assessment of narrative write-up” to “veryorganized”. A review is usually reviews, study identification and quality assessment the qualitative studies9, 10 while the Effective Public Health structured according to the following steps6: techniques vary. For example, if a review aims to catalogue Practice Project (EPHPP) is an example of a quantitative

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Table-1: Major types of reviews in the health research. • Requires all the included studies to be sufficiently similar.

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JNHFB Jul 2016 Ahmed S et al.

2. Critical review 6. Qualitative systematic review A critical review is not just a summary of the literature; Qualitative studies have gained considerable importance in rather, it demonstrates extensive research and quality current medical and social science literature. A qualitative evaluation. Authors of critical reviews do not need to systematic review is an approach used to integrate and mention every single element from the source literature, but compare the findings from qualitative literature on a specific 17 instead extract the most important ideas from the sources topic . cited13. Generally, the findings of critical reviews are typically hypotheses or models. 7. Realist review A realist review arose from the need to deal with complex 3. Scoping review interventions and heterogeneity of study design, study 18 A scoping review focuses on identifying the nature and settings, context, outcome measures etc . Systematic extent of literature available on any specific topic. It is reviews are ideal for simple and single interventions, similar to a systematic review with the exception that it however, in reality, healthcare professionals and policy provides a quality assessment of primary literature. This makers usually deal with multiple interventions in complex type of review unveils the scope of future research and may scenarios. Instead of a straightforward answer to a question, lead to conducting a systematic review on the topic to gain a realist review will provide a rich, detailed and practical more specific knowledge14. understanding of complex social interventions.

Table – 3: Major types of reviews: their strengths and weaknesses

Type Strength Weakness

Literature Identifies what has been Lacks an explicit intent to review accomplished previously maximize scope or analyse data collected

Critical A good source for a quick Lack of a systematic review overview stock of search can create bias in knowledge on any topic the aggregate of literature Often attempts to resolve for synthesis. competing schools of thoughts

48 Conducting a Literature Review in Health Research: Basics of the Approach Ahmed S et al.

Scoping Inform researchers, Lack of quality review policymakers, or assessment risks the stakeholders about the inclusion of studies based extent of work that has on their existence rather already been done than their intrinsic quality Identify any potential gaps in the research domain Informs as to whether a full systematic review is needed

Systematic Seek to draw together all As with any subjective review known knowledge review, there is the (quantitative, qualitative problem of selection bias, and mixed-method) on a where contradictory topic research is omitted

Meta-analysis Assimilation of conclusive Inappropriateness of and statistically significant combining studies not studies create a strong similar enough weakens evidence base for practice the finding Overcomes small sample sizes of individual studies. Increases precision in estimating effects.

Qualitative Compliments research The method is still in systematic evidence with two essential infancy and there are review components of evidence debates about practice: user-reported and appropriateness of the practitioner-observed methodology considerations Realist Systematic involvement of Because of limited review papers concerning description of context and stakeholders, which ensures mechanism inthe studies, that relevance is maintained context-mechanism- Focus on explanation rather outcome con gurations than judgement need to be constructed through argumentation analysis, which is complicated and time consuming

Review of Allows the reader a quick A useful review of reviews overview (and an reviews requires pre- exhaustive list) of reviews existence of the narrower relevant to thedecision at component reviews hand

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Table – 4: Examples of each type of major review and objective of those studies.

Types PMID Author Title Objective of this paper

Literature 25515274 Azad MC et al. Sleep Disturbances among Medical This review summarized literature on review Students: A Global Perspective sleep problems among undergraduate medical students around the world.

Critical 18031221 Kovats RS and Heat stress and public health: a This article reviewed epidemiological review Hajat S critical review information on the impacts of heat waves and hot weather. It also described the implications of this research for public health.

Scoping 26364053 Ahmed S et al. Barriers to Access of Primary This scoping review of the literature review Healthcare by Immigrant Populations was conducted to map the existing in Canada: A Literature Review. literature about the barriers to access primary healthcare by immigrants in Canada. It also determined the extent and types of evidence available on this topic and to identified the gaps in the literature for future research.

Systematic 23776544 Braun R et al. Community health workers and This review systematically reviewed review mobile technology: a systematic the literature on the use of mobile review of the literature. technology to help improve the services delivered by community health workers. It also described the health of the communities they serve.

Meta- 18786971 Sofi F et al. Adherence to Mediterranean diet and This meta-analysis reviewed analysis health status: meta-analysis prospective cohort studies in primary care setting that analysed the relation between Mediterranean diet, mortality, and incidence of chronic diseases.

Qualitative 26143357 Mikkonen K et al. Culturally and linguistically diverse This systematic review analyzed systematic healthcare students' experiences of qualitative studies that were aimed to review learning in a clinical environment: A identify clinical learning experience of systematic review of qualitative culturally and linguistically diverse studies. healthcare students.

Realist 25535014 Paternotte E et al. Factors influencing intercultural This study provided an overview of review doctor-patient communication: a how intercultural communication realist review. between doctors and patients works.

Review of 24165786 Mickan S et al. Evidence of effectiveness of health This study reviewed the systematic reviews care professionals using handheld reviews about the effectiveness of computers: a scoping review of handheld computers in clinical work by systematic reviews. healthcare professionals.

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Closing Remarks ORION, COREQ, QUOROM, REMARK... and CON- Depending on the needs and approaches, different genres of SORT: for whom does the guideline toll? Journal of reviews have arisen. The typology of reviews presented in clinical epidemiology. 2009;62(6):594. this article is a brief description of major types of reviews. 9. O’Brien BC, Harris IB, Beckman TJ, Reed DA, Cook With increasing focus on synthesizing evidence through a DA. Standards for reporting qualitative research: a systematic review for generating direction and recommen- synthesis of recommendations. Academic Medicine. dations for best practice, healthcare researchers need to have 2014;89(9): 1245-51. a clear understanding of the steps required for conducting 10. Tong A, Sainsbury P, Craig J. Consolidated criteria for appropriate reviews. In this manuscript we have provided a reporting qualitative research (COREQ): a 32-item brief step-by-step explanation of the basic principles and checklist for interviews and focus groups. Internation- typology of literature reviews al Journal for Quality in Health Care. 2007;19(6):349.

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