A systematic review is a type of secondary evidence that summarises research that has already been published.
Systematic reviews, according to Wright, et al., are defined as a:
“review of the evidence on a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant primary research, and to extract and analyze data from the studies that are included in the review.”
What are Systematic Reviews? (3:23 min) by Cochrane (YouTube)
When conducting a systematic review it is important to ask a question that can be answered through use of evidence, rather than subjective judgment. In evidence based practice, systematic reviews are considered one of the highest levels of information.
A systematic review may sometimes include a meta-analysis. A meta-analysis is the use of statistical methods to combine data from studies included in a systematic review. Not all systematic reviews include a meta-analysis.
Image: What's In a Name?: the Difference Between a Systematic Review and a Literature Review and Why It Matters (pdf) by Lynn Kysh / CC-BY 4.0
Image: What's In a Name?: the Difference Between a Systematic Review and a Literature Review and Why It Matters (pdf) by Lynn Kysh / CC-BY 4.0
Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. Types of evidence synthesis include:
A broad term referring to reviews with a wide scope and non-standardized methodology.
Applies systematic review methodology within a time-constrained setting.
Systematically and transparently collects and categorizes existing evidence on a broad topic or set of research questions.
Reviews other systematic reviews on a topic.
A methodical and comprehensive literature synthesis focused on a well-formulated research question.
A statistical technique for combining the findings from disparate quantitative studies.
"What type of review is right for you?" by Cornell University Library is licensed under CC BY 4.0
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. https://doi.org/10.1111/j.1471-1842.2009.00848.x
Cornell University Library has developed a decision tree that assists in identifying the types of reviews.
Image: "What type of review is right for you?" by Cornell University Library is licensed under CC BY 4.0
Do you want to gather all the evidence on a particular research topic?
No: Do a Literature (Narrative) Review.
Yes: Do you have 3 or more people to work on the review?
No: More intensive reviews usually require a multi-person team for unbiased article screening.
Yes: Do you have 12–18 months to complete a review?
No: Do a Rapid Review.
Yes: Do you have a broad topic or multiple research questions?
Yes: Do a Scoping Review.
No: Do you want to review other published systematic reviews on your topic?
Yes: Do an Umbrella Review.
No: Do you have a well-formulated research question?
No: Systematic reviews are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making and to identify gaps in research. They require a well-formulated research question.
Yes: Do a Systematic Review.
Will you use statistical methods to objectively evaluate, synthesize, and summarize results?
No: A meta-analysis will not be needed.
Yes: Do a Meta-Analysis.
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