|The purpose of this guide is to connect you with useful information and resources for embarking on a systematic review or other type of synthesis. Information about conducting standard literature reviews can be found here.|
Note: some hyperlinked resources are provided by Queen's University Library and may not be available to non-affiliates. Queen's affiliates viewing this guide from off-site may need to login via off-campus access to open resources and view full-text articles.
CIHR defines synthesis 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 and may synthesize qualitative or quantitative results.
The evolution of syntheses:
When systematic reviews were the first type of synthesis to appear in the health care literature back in the 1970s, the main objective was to synthesize quantitative research studies. Limitations of traditional systematic reviews and meta-analyses have led to the adaptation of syntheses to include: qualitative systematic reviews, mixed-methods reviews, rapid reviews, network meta-analyses, scoping reviews and realist reviews. While many syntheses begin with a clear question, their methodologies and the types of research evidence synthesized to answer the question can be quite different.
Deciding what type of syntheses to conduct:
To help determine the most appropriate type of synthesis for your research question and purpose, you may find it helpful to consult the following articles.
Overview of 12 knowledge synthesis methods that go beyond the traditional systematic review (Kaster et al., 2016):
Fig. 1. Conceptual algorithm to optimize selection of a knowledge synthesis method for answering a research question.
A systematic review attempts to identify, select, synthesize, and appraise all evidence for a given research question in a systematic and transparent manner.
*Important: before embarking on a systematic review, make sure that 1) a recent review on the same topic has not already been published, and 2) that a review protocol has not already been registered for the same topic.
To check for systematic reviews that have already been published on your topic, search databases such as Ovid MEDLINE/PubMed, Embase, PsycINFO, CINAHL, and even Google Scholar to catch any journal content that is not covered in these databases. You can also search Epistemonikos for published systematic reviews, a freely available resource that attempts to identify all of the systematic reviews relevant for health decision-making. To check for registered (i.e. forthcoming) systematic reviews, search PROSPERO, the international prospective register of systematic reviews. You can also search for registered protocols by systematic review collaborations such as Cochrane, Campbell and the Joanna Briggs Institute. When you are confident that your research will not be duplicating efforts, you are ready to begin your own review.
Eight stages of a systematic review and meta-analysis (Uman, 2011):
Most often the type of systematic review conducted will depend on the review question. For example, systematic reviews of healthcare interventions are often quantitative reviews that include research studies in the form of randomized controlled trials. Systematic reviews of patient experiences are generally qualitative reviews that may include qualitative and mixed methods research studies. Mixed methods reviews are utilized to address the limitations of single method reviews, which are frequently too narrow in scope (Peters et al., 2015). "By including diverse forms of evidence from different types of research, mixed methods reviews attempt to maximize the findings - and the ability of those findings to inform policy and practice" (Peters et al., 2015, p. 5).
Cochrane describes the five types of Cochrane Reviews:
Topic: The review topic will impact the amount of time required to conduct the review. For example, a systematic review on the effectiveness of a relatively new drug therapy may require less time to complete if the search yields a low number of results to screen and if the review itself only includes a small number of studies.
Searching: The amount of time needed to complete this component of the review will depend on: how straight-forward or complex the topic is, the number and type of resources that will be searched (refer to Where to Search), and the searcher's level of expertise. Working with an experienced librarian is a best practice recommendation (refer to Librarian Support).
Review team: Estimating how long it will take to complete a systematic review will depend on the size of the review team and how available the team members are to work on the review. Researchers often have competing priorities throughout the duration of the systematic review that can delay the process.
|"Scoping studies aim to map rapidly the key concepts underpinning a research area and the main sources and types of evidence available, and can be undertaken as stand-alone projects in their own right, especially where an area is complex or has not been reviewed comprehensively before" (Mays et al., 2001, p. 194).|
The following articles describe the purpose and methods of scoping reviews in detail:
Peters, M. D., Godfrey, C. M., Khalil, H., McInerney, P., Parker, D., & Soares, C. B. (2015). Guidance for conducting systematic scoping reviews. International journal of evidence-based healthcare, 13(3), 141-146.
Arksey, H., & O'Malley, L. (2005). Scoping studies: towards a methodological framework. International Journal of Social Research Methodology, 8(1), 19-32. doi:10.1080/1364557032000119616
Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91-108.
Greenhalgh, T., & Peacock, R. (2005). Effectiveness and efficiency of search methods in systematic reviews of complex evidence: audit of primary sources. BMJ: British Medical Journal, 331(7524), 1064-1065.
Higgins, J.P.T. & Green, S. (Eds.). (2011). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration. Available from www.handbook.cochrane.org.
Institute of Medicine. (2011). Finding what works in health care: standards for systematic reviews. Washington, DC: The National Academies Press.
Kastner, M., Antony, J., Soobiah, C., Straus, S. E., & Tricco, A. C. (2016). Conceptual recommendations for selecting the most appropriate knowledge synthesis method to answer research questions related to complex evidence. Journal of Clinical Epidemiology, 73, 43-49.
Koffel, J. B. (2015). Use of recommended search strategies in systematic reviews and the impact of librarian involvement: A cross-sectional survey of recent authors. PLoS ONE, 10(5), 1–13.
Mays, N., Roberts, E., & Popay, J. (2001). Synthesising research evidence. Studying the Organisation and Delivery of Health Services: Research Methods, 188-220.
McGowan, J., & Sampson, M. (2005). Systematic reviews need systematic searchers. Journal of the Medical Library Association, 93(1), 74.
Meert, D., Torabi, N., & Costella, J. (2016). Impact of librarians on reporting of the literature searching component of pediatric systematic reviews. Journal of the Medical Library Association : JMLA, 104(4), 267–277. https://doi.org/10.3163/1536-5050.104.4.004
Moher D., Stewart L. & Shekelle P. (2015). All in the family: systematic reviews, rapid reviews, scoping reviews, realist reviews, and more. Syst Rev, 4(1):1-2.
Petticrew, M. (2001). Systematic reviews from astronomy to zoology: myths and misconceptions. BMJ: British Medical Journal, 322(7278), 98.
Rethlefsen, M. L., Farrell, A. M., Osterhaus Trzasko, L. C., & Brigham, T. J. (2015). Librarian co-authors correlated with higher quality reported search strategies in general internal medicine systematic reviews. Journal of Clinical Epidemiology, 68(6), 617–626. https://doi.org/10.1016/j.jclinepi.2014.11.025
Saleh, A. A., Ratajeski, M. A., & Bertolet, M. (2014). Grey literature searching for health sciences systematic reviews: a prospective study of time spent and resources utilized. Evidence Based Library and Information Practice, 9(3), 28-50.
Tricco, A. C., Lillie, E., Zarin, W., O’Brien, K., Colquhoun, H., Kastner, M., ... & Kenny, M. (2016). A scoping review on the conduct and reporting of scoping reviews. BMC medical research methodology, 16(1), 1.