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Beyond Medline: reducing bias through extended systematic review search.
Isabelle Savoie1, Diane Helmer, Carolyn J Green
1British Columbia Office of Health Technology Assessment, Centre for Health Services and Policy Research, University of British Columbia, Vancouver, Canada.
Summary
Extended search methods, including specialized databases and trial registries, significantly improve the identification of randomized controlled trials (RCTs) for systematic reviews. These methods uncover additional RCTs missed by major databases, enhancing review comprehensiveness.
Area of Science:
- Medical Research Methodology
- Evidence Synthesis
- Information Science
Background:
- Systematic reviews rely on comprehensive identification of randomized controlled trials (RCTs).
- Major databases may not capture all relevant RCTs, potentially limiting the scope of systematic reviews.
- Extended search strategies are employed to supplement traditional database searches.
Purpose of the Study:
- To evaluate the sensitivity and precision of various extended search methods for identifying RCTs.
- To compare the effectiveness of different extended search techniques in the context of systematic reviews.
Main Methods:
- A prospective analysis of extended search methods was conducted across two systematic reviews.
- Methods evaluated included specialized databases/trial registries, reference lists, hand-searching, personal communication, and internet searches.
- Sensitivity and precision were calculated against a gold standard of all identified RCTs.
Main Results:
- Extended search methods identified 94 additional RCTs not found in major databases.
- Specialized databases and trial registries demonstrated the highest sensitivity and precision.
- A significant number of RCTs were indexed in major databases but missed by standard searches.
Conclusions:
- Extended searching is crucial for identifying a broader range of RCTs for systematic reviews.
- Specialized databases and trial registries are highly effective supplementary search tools.
- Inaccuracies or delays in database indexing may explain missed RCTs, warranting further investigation.
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