Systematic Reviews and Review Types: What is an Overview of Reviews?

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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, Meta-Meta-analysis

What is an Overview of Reviews?

It is a systematic review of systematic 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.” Examines two or more systematic reviews or evidence syntheses. 

Source: Blackwood D (2016)

Overviews of Reviews are best designed for:

  • Synthesizing and combining relevant data from existing systematic reviews or meta-analyses to make better decisions.
  • To provide clinical decision makers with the evidence they need when there are too many systematic reviews for them to keep up with for an intervention.
  •  

What is an Overview of Reviews? Outline of Stages

Timeframe: Approximately 12 months or less.   *Varies beyond the type of review. Depends on many factors such as but not limited to: resources available, the quantity and quality of the literature, and the expertise or experience of reviewers” (Grant et al. 2009)

Question: Overviews are broader in scope but the question is still specific and well-defined, can use PICO to formulate the question. 

Sources and searches: Only locating the highest level of evidence of published or unpublished:

  1. Systematic Reviews or
  2. Meta-analyses
  3. Other types of evidence synthesis that meets inclusion criteria

Only identifies other reviews or evidence syntheses. It may be likely to limit the search from 1990 to current since there were few research syntheses published prior.

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: Present outcome data exactly as they appear or re-analyze the outcome data in a different way. 

Limitations of an Overview of Reviews

  • Should not summarize but should synthesize and integrate the evidence of other systematic reviews.
  • An Overview of Reviews in not easier than a regular systematic review, treat the process like a regular systematic review.

Resources:

Cochrane Collaboration: Overviews of Reviews 

JBI Manual: Umbrella Reviews (2020)

Aromataris E, Fernandez R, Godfrey C, et al.  Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach.  International journal of evidence-based healthcare.  2015;13:3.  

Smith V, Devane D, Begley C and M Clarke.  Methodology in conducting a systematic review of systematic reviews of healthcare interventions.  BMC Medical Research Methodology. 2011;11:15.

Overviews of systematic reviews: development and evaluation of methods: Thematic Series published in BMC Systematic Reviews

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