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* Booth A, Sutton A, Papaioannou D. Systematic approaches to a successful literature review. 2nd edition. Los Angeles, CA: Sage, 2016. (p.36)
A literature review provides an overview of what's been written about a specific topic. It is a generic term. There are many different types of literature reviews which can cover a wide range of subjects at various levels of completeness and comprehensiveness. Choosing the type of review you wish to conduct will depend on the purpose of your review, and the time and resources you have available.
This page will provide definitions of some of the most common review types in the health sciences and links to relevant reporting guidelines or methodological papers.
Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal. 2009 Jun 1;26(2):91-108.
Traditional (narrative) literature reviews provide a broad overview of a research topic with no clear methodological approach. Information is collected and interpreted unsystematically with subjective summaries of findings. Authors aim to describe and discuss the literature from a contextual or theoretical point of view. Although the reviews may be conducted by topic experts, due to preconceived ideas or conclusions, they could be subject to bias. This sort of literature review can be appropriate if you have a broad topic area, are working on your own, or have time constraints.
Green BN, Johnson CD, Adams A. Writing narrative literature reviews for peer-reviewed journals: secrets of the trade. Journal of Chiropractic Medicine. 2006;5(3):101-117. doi:10.1016/S0899-3467(07)60142-6.
Ferrari R. Writing narrative style literature reviews. Medical Writing. 2015 Dec 1;24(4):230-5.
Greenhalgh T, Thorne S, Malterud K. Time to challenge the spurious hierarchy of systematic over narrative reviews? European journal of clinical investigation. 2018;48:e12931.
Literature reviews using systematic methods fall under the knowledge synthesis umbrella. Knowledge synthesis can be defined as “…the contextualization and integration of research findings of individual research studies within the larger body of knowledge on the topic. A synthesis must be reproducible and transparent in its methods, using quantitative and/or qualitative methods. It could take the form of a systematic review, follow the methods developed by the Cochrane Collaboration, result from a consensus conference or expert panel or synthesize qualitative or quantitative results. Realist syntheses, narrative syntheses, meta-analyses, meta-syntheses and practice guidelines are all forms of synthesis.” (Canadian Institutes of Health Research. (2016, July 28). Knowledge Translation. Retrieved April 26, 2018, from http://www.cihr-irsc.gc.ca/e/29418.html. )
Grimshaw J. A Guide to Knowledge Synthesis [Internet]. CIHR. Canadian Institutes of Health Research; 2010.
Canadian Institutes of Health Research. Synthesis Resources [Internet]. CIHR. Canadian Institutes of Health Research; 2013.
Kastner M, Tricco AC, Soobiah C, et al. What is the most appropriate knowledge synthesis method to conduct a review? Protocol for a scoping review. BMC Medical Research Methodology. 2012;12:114. doi:10.1186/1471-2288-12-114.
Kastner M, Antony J, Soobiah C, Straus SE, Tricco AC. Conceptual recommendations for selecting the most appropriate knowledge synthesis method to answer research questions related to complex evidence. Journal of Clinical Epidemiology. 2016;73:43-49.
A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making. (See Section 1.2 in the Cochrane Handbook for Systematic Reviews of Interventions.)
A systematic review is not the same as a traditional (narrative) review or a literature review. Unlike other kinds of reviews, systematic reviews must be as thorough and unbiased as possible, and must also make explicit how the search was conducted. Systematic reviews may or may not include a meta-analysis.
On average, a systematic review project takes a year. If your timelines are shorter, you may wish to consider other types of synthesis projects or a traditional (narrative) review. See suggested timelines for a Cochrane Review for reference.
Greyson D, Rafferty E, Slater L, et al. Systematic review searches must be systematic, comprehensive, and transparent: a critique of Perman et al. BMC public health. 2019;19:153.
Ioannidis J. P. (2016). The Mass Production of Redundant, Misleading, and Conflicted Systematic Reviews and Meta-analyses. The Milbank quarterly, 94(3), 485-514.
A subset of systematic reviews. Meta-analysis is a technique that statistically combines the results of quantitative studies to provide a more precise effect of the results.
"..a form of knowledge synthesis that addresses an exploratory research question aimed at mapping key concepts, types of evidence, and gaps in research related to a defined area or field by systematically searching, selecting and synthesizing existing knowledge." (Colquhoun, HL et al., 2014)
Arksey, H., & O'Malley, L. (2005). Scoping studies: Towards a methodological framework. International Journal of Social Research Methodology: Theory and Practice, 8 (1), 19-32. doi:10.1080/1364557032000119616.
Colquhoun, H. L., Levac, D., O'Brien, K. K., Straus, S., Tricco, A. C., Perrier, L., . . . Moher, D. (2014). Scoping reviews: Time for clarity in definition, methods, and reporting. Journal of Clinical Epidemiology, 67(12), 1291-1294. doi:10.1016/j.jclinepi.2014.03.013.
Peters MD, Godfrey CM, Khalil H, McInerney P, Parker D, Soares CB. Guidance for conducting systematic scoping reviews. Int.J.Evid Based.Healthc. 2015 Sep;13(3):141-146.
Peters MDJ, Godfrey C, McInerney P, Baldini Soares C, Khalil H, Parker D. Chapter 11: Scoping Reviews. In: Aromataris E, Munn Z (Editors). Joanna Briggs Institute Reviewer's Manual. The Joanna Briggs Institute, 2017.
Tricco AC, Lillie E, Zarin W, O'Brien KK, Colquhoun H, Levac D, et al. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med. [Epub ahead of print ] doi: 10.7326/M18-0850.
“…a type of knowledge synthesis in which systematic review processes are accelerated and methods are streamlined to complete the review more quickly than is the case for typical systematic reviews. Rapid reviews take an average of 5–12 weeks to complete, thus providing evidence within a shorter time frame required for some health policy and systems decisions.” (Tricco AC et al., 2017)
Ganann R, Ciliska D, Thomas H. Expediting systematic reviews: methods and implications of rapid reviews. Implementation Science : IS. 2010;5:56. doi:10.1186/1748-5908-5-56.
Langlois EV, Straus SE, Antony J, King VJ, Tricco AC. Using rapid reviews to strengthen health policy and systems and progress towards universal health coverage. BMJ Global Health. 2019;4:e001178.
Tricco AC, Langlois EV, Straus SE, editors. Rapid reviews to strengthen health policy and systems: a practical guide. Geneva: World Health Organization; 2017. Licence: CC BY-NC-SA 3.0 IGO.
Watt A, Cameron A, Sturm L, Lathlean T, Babidge W, Blamey S, et al. Rapid reviews versus full systematic reviews: An inventory of current methods and practice in health technology assessment. International Journal of Technology Assessment in Health Care. 2008;24(2):133-9.
“Clinical practice guidelines are systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances.” Source: Institute of Medicine. (1990). Clinical Practice Guidelines: Directions for a New Program, M.J. Field and K.N. Lohr (eds.) Washington, DC: National Academy Press. Page 38.
–Disclosure of any author conflicts of interest
Alonso-Coello, P., Oxman, A. D., Moberg, J., Brignardello-Petersen, R., Akl, E. A., Davoli, M., ... & Guyatt, G. H. (2016). GRADE Evidence to Decision (EtD) frameworks: a systematic and transparent approach to making well informed healthcare choices. 2: Clinical practice guidelines. bmj, 353, i2089.
Pawson R, Greenhalgh T, Harvey G, Walshe K. Realist review - a new method of systematic review designed for complex policy interventions. Journal of Health Services Research & Policy. 2005;10:21-34.
Rycroft-Malone J, McCormack B, Hutchinson AM, et al. Realist synthesis: illustrating the method for implementation research. Implementation science : IS. 2012;7:33.
Wong G, Greenhalgh T, Westhorp G, Pawson R. Realist methods in medical education research: what are they and what can they contribute? Medical Education. 2012;46(1):89-96.
"Mixed-methods systematic reviews can be defined as combining the findings of qualitative and quantitative studies within a single systematic review to address the same overlapping or complementary review questions." (Harden A, 2010)
Harden A. Mixed-Methods Systematic Reviews: Integrating quantitative and qualitative findings. NCDDR:FOCUS. 2010.
Pluye P, Hong QN. Combining the power of stories and the power of numbers: mixed methods research and mixed studies reviews. Annual review of public health. 2014;35:29-45.
Pearson A, White H, Bath-Hextall F, Salmond S, Apostolo J, Kirkpatrick P. A mixed-methods approach to systematic reviews. International journal of evidence-based healthcare. 2015;13:121-131.
The Joanna Briggs Institute 2014 Reviewers Manual: Methodology for JBI Mixed Methods Systematic Reviews.
There are various methods for integrating the results from qualitative studies. "Systematic reviews of qualitative research have an important role in informing the delivery of evidence-based healthcare. Qualitative systematic reviews have investigated the culture of communities, exploring how consumers experience, perceive and manage their health and journey through the health system, and can evaluate components and activities of health services such as health promotion and community development." (Lockwood C et al., 2015)
Ring N, Jepson R, Ritchie K. Methods of synthesizing qualitative research studies for health technology assessment. International Journal of Technology Assessment in Health Care. 2011;27:384-390.
Lockwood C, Munn Z, Porritt K. Qualitative research synthesis: methodological guidance for systematic reviewers utilizing meta-aggregation. International journal of evidence-based healthcare. 2015;13:179-187.
France EF, Cunningham M, Ring N, et al. Improving reporting of meta-ethnography: The eMERGe reporting guidance. Journal of advanced nursing. 2019.
Seers K. Qualitative systematic reviews: their importance for our understanding of research relevant to pain. Br J Pain. 2015;9(1):36-40.
Barnett-Page E, Thomas J. Methods for the synthesis of qualitative research: a critical review. BMC Med Res Methodol. 2009;9:59. Published 2009 Aug 11. doi:10.1186/1471-2288-9-59.
Thomas J, Harden A. Methods for the thematic synthesis of qualitative research in systematic reviews. BMC Med Res Methodol. 2008;8:45. Published 2008 Jul 10. doi:10.1186/1471-2288-8-45
Lewin S, Booth A, Glenton C, et al. Applying GRADE-CERQual to qualitative evidence synthesis findings: introduction to the series. Implementation science : IS. 2018;13:2.
"Narrative synthesis refers to an approach to the systematic review and synthesis of findings from multiple studies that relies primarily on the use of words and text to summarise and explain the findings of the synthesis. Whilst narrative synthesis can involve the manipulation of statistical data, the defining characteristic is that it adopts a textual approach to the process of synthesis to ‘tell the story’ of the findings from the included studies." (Popay J, 2006)
Tricco AC, Soobiah C, Antony J, et al. A scoping review identifies multiple emerging knowledge synthesis methods, but few studies operationalize the method. Journal of Clinical Epidemiology. 2016;73:19-28.
Popay J, Roberts H, Sowden A, Petticrew M, Arai L, Rodgers M, et al. Guidance on the conduct of narrative synthesis in systematic reviews. Lancaster: ESRC Research Methods Programme; 2006.
Snilstveit B, Oliver S, Vojtkova M. Narrative approaches to systematic review and synthesis of evidence for international development policy and practice. Journal of development effectiveness. 2012 Sep 1;4(3):409-29.
Lucas PJ, Baird J, Arai L, Law C, Roberts HM. Worked examples of alternative methods for the synthesis of qualitative and quantitative research in systematic reviews. BMC medical research methodology. 2007 Dec;7(1):4.
Ryan R. Cochrane Consumer sand Communication Review Group. Cochrane Consumers and Communication Review Group: data synthesis and analysis. June 2013.