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Systematic Reviews & Other Review Types

What is an Overview of Reviews?

"The intent of this kind of review is to include systematic reviews or meta-analyses as the main study type and thus examine only the highest level of evidence." 

"The aim is not to repeat the searches, assess study eligibility, and assess risk of bias from included studies but rather to provide an overall picture of findings."

Source: Blackwood D (2016)

Overviews of Reviews are used:

  • For synthesizing and combining relevant data from existing systematic reviews or meta-analyses to make better decisions.
  • For providing clinical decision makers with the evidence they need when there are too many systematic reviews for them to keep up with for an intervention.
  • When there needs to be a rapid evidence synthesis for decision-makers but you need higher quality evidence due to limitations of the rapid review methodology.

How an Overview of Reviews differs from a Systematic Review

Timeframe: Approximately 12 months or less. 

Question: A broad or narrow PICO of 1 or more interventions.

Sources and searches: Only locating the highest level of evidence of published or unpublished:

  1. Systematic Reviews or
  2. Meta-analyses

The aim is not to identify any new studies.

Selection: Based upon clear inclusion/exclusion criteria and outcome measures defined a priori. 

Appraisal: Critical Appraisal of systematic reviews done by at least two independent reviewers using the appropriate tool.  

Synthesis: May need to alter the meta-analyses in the included reviews or re-synthesize the data while extracting and combining the relevant data.  A final 'Summary of Evidence' table should be present.

Limitations of an Overview of Reviews

  • Is often mistaken as just a summary of reviews, but it must include the re-synthesis of data.
  • Sometimes confused with being as quick as a rapid review
  • Overviews of Reviews also do not include study types other than systematic reviews and meta-analyses.
  • Requires a systematic review expert to critically appraise systematic reviews.
  • Is likely to limit the search from 1990 to current since there were few research syntheses published prior.

Other names for an Overview of Reviews

Systematic Review of Systematic Reviews, Umbrella Review, Review of Reviews, Summary of Systematic Reviews, Synthesis of Reviews, Review of Systematic Reviews, Review of Reviews, Review of Meta-analyses, Meta-review, Systematic Meta-review

Temple Attribution

Adapted with permission from Temple University Libraries. https://guides.temple.edu/systematicreviews

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