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Systematic Review: a high-level overview of primary research on a particular research question that tries to identify, select, synthesize and appraise all high quality research evidence relevant to that question in order to answer it. – Definition from Cochrane Collaboration
Meta-Analysis: a quantitative statistical analysis of several separate but similar experiments or studies in order to test the pooled data for statistical significance [often found within systematic reviews, but not the same]. – Definition from www.merriam-Webster.com
All meta-analyses should be part of a systematic review, but not all systematic reviews will include a meta-analysis.
Systematic reviews are usually researched and written as a group to remove any questions, biases, or doubts about a specific item. A systematic review really should NOT be attempted by 1 person alone, there could be too many validity/reliability questions raised by reviewers.
Beginning Evidence Based Medicine (EBM) practitioners often have difficulty distinguishing between the evidence and the evidence-based literature. MEDLINE adds to the confusion because it classifies both systematic reviews of the literature and the more common narrative reviews as Review [Publication Type].
Systematic reviews seek to answer clearly formulated questions by using rigorous, explicit protocols to identify, select and appraise relevant research studies; and to collect and analyze data from the selected studies. To minimize bias, systematic reviews include or exclude evidence on the basis of explicit quality criteria.They may incorporate meta-analysis.
Narrative reviews articles may be evidence-based, but they are NOT evidence (research). They usually lack systematic search protocols or explicit criteria for selecting and appraising evidence. Instead, they rely on experts to gather evidence and synthesize findings.
|Investigate a clearly defined topic or question.||Intended to provide an overview of an area.|
|Literature is gathered using explicit search protocols.||Explicit, systematic literature search protocol not used.|
|Studies selected for the review using a protocol that specifies inclusion, exclusion criteria.||Studies used to support the reviewers' recommendations are not selected according to an explicit, predetermined protocol.|
|Data from primary study may be synthesized in a meta-analysis. Evidence "grades" may be applied to individual studies.||May use a level of evidence rating system to "grade" the quality and strength of individual studies.|
|When evidence is lacking, the authors usually recommend further research.||When evidence is lacking, the authors make recommendations based on their opinions and experience. Recommendations may be "graded" based on the consistency and strength of the underlying evidence.|
Do I have a clearly defined clinical question with established inclusion and exclusion criteria?
Do I have a team of at least three people assembled?
Do I have time to go through as many search results as we might find?
Do I have resources to get foreign-language articles appropriately translated? (Note that exclusion of foreign-language articles is an inherent bias.)
Do I have the statistical resources to analyze and pool data?
If you answered “No” to any of the first four questions, a traditional literature review will be more appropriate to do. If you answered “No” to the last question, a meta-analysis will not be an appropriate methodology for your review.
Taken and adapted from Mayo Clinical Library Blog
Email: sysrev <at> hsl.wisc.edu