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Search for unpublished data by systematic reviewers: an audit
Hedyeh Ziai1,2, Rujun Zhang1,3, An-Wen Chan4,5
1Keenan Research Centre, Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Canada.
BMJ Open
|October 9, 2017
Summary
Many systematic reviews miss unpublished data, potentially skewing results. Almost half of reviews assessing publication bias found it, indicating a need for more comprehensive data searching in systematic reviews.
Area of Science:
- Medical Research Methodology
- Evidence Synthesis
- Biostatistics
Background:
- Systematic reviews are crucial for evidence synthesis.
- Publication bias can distort findings.
- Searching for unpublished data is key to minimizing bias.
Purpose of the Study:
- To audit systematic reviews for the use of unpublished data.
- To assess the prevalence of publication bias assessment.
- To determine the impact of unpublished data exclusion.
Main Methods:
- Audit of systematic reviews published in 2013.
- Searched major medical journals and the Cochrane Library.
- Two reviewers extracted data on unpublished data searches and bias assessment.
Main Results:
- 36% of reviews did not search for unpublished data.
- 89% of those searching found unpublished data.
- 33% assessed publication bias, with 40% finding evidence of it.
Conclusions:
- A significant portion of systematic reviews omit unpublished data.
- Publication bias is likely present in many reviews.
- Excluding unpublished data can lead to biased efficacy and safety estimates.
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