“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.”
- Cochrane Library, About Cochrane Systematic Reviews and Protocols
“Library books,” CCAC North Library
Systematic Reviews are comprehensive analyses of all the scientific research on a specific question. They answer the question: what does the evidence say about this medical issue?
Systematic reviews are crucial to medical practice and research. They are a valuable resource for clinicians deciding on treatments, and they also reveal gaps in current research.
A systematic review is not the same as a narrative review or a literature review. Unlike other kinds of reviews, systematic ones must be as thorough and unbiased as possible, and must also make explicit how the search was conducted.
“Research - IMG_1367,” Nicola
A true systematic review:
If you are a student, you're probably not conducting a systematic review in the true sense, but are working on a systematic review-like project.
A scoping study can be defined as:"..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." (from: 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,(12), 1291-1294. ).
Common reasons for conducting a scoping study:
(from Arksey, H., O'Malley, L. (2005). Scoping studies: towards a methodological framework. International Journal of Social Research Methodology, 8(1): 19-32.)
Scoping studies typically involve six steps:
Scoping studies differ from systematic reviews in several ways:
|Scoping review||Systematic review|
|Research question||Broadly defined||Highly focused|
|Inclusion/Exclusion criteria||Developed post hoc at study selection stage||Developed at protocol stage|
|Study selection||All study types||Defined study types|
|Data extraction||“Charts” data according to key issues, themes, etc.||Synthesizes & aggregates findings
HOWEVER both systematic reviews and scoping reviews require comprehensive and structured searches of the literature to maximize recall and decrease bias.
Guide to Knowledge Synthesis from Canadian Institutes of Health Research (CIHR)
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
|Narrative review||Evidence Synthesis|
|Search methods||not systematic, nor validated, nor peer reviewed||systematic, highly structured to minimize bias ; conducted much like other scientific studies|
|Inclusion/Exclusion criteria||Not explicitly stated||Included in protocol or developed post hoc|
|Bias||potential for authors to selectively include or exclude studies to support a position||attempts to minimize bias based on protocol, non-selective reporting of outcomes and transparent and reproducible search strategies|
|Replication & updating||Difficult since search methodology not reported in detail in methods section nor included in full in the appendices||Designed to be reproducible and facilitate updating