Optimizing literature search in systematic reviews - are MEDLINE, EMBASE and CENTRAL enough for identifying effect studies within the area of musculoskeletal disorders?

Background: When conducting systematic reviews, it is essential to perform a comprehensive literature search to identify all published studies relevant to the specific research question. The Cochrane Collaborations Methodological Expectations of Cochrane Intervention Reviews (MECIR) guidelines state that searching MEDLINE, EMBASE and CENTRAL should be considered mandatory. The aim of this study was to evaluate the MECIR recommendations to use MEDLINE, EMBASE and CENTRAL combined, and examine the yield of using these to find randomized controlled trials (RCTs) within the area of musculoskeletal disorders. Methods: Data sources were systematic reviews published by the Cochrane Musculoskeletal Review Group, including at least five RCTs, reporting a search history, searching MEDLINE, EMBASE, CENTRAL, and adding reference-and hand-searching. Additional databases were deemed eligible if they indexed RCTs, were in English and used in more than three of the systematic reviews. Relative recall was calculated as the number of studies identified by the literature search divided by the number of eligible studies i.e. included studies in the individual systematic reviews. Finally, cumulative median recall was calculated for MEDLINE, EMBASE and CENTRAL combined followed by the databases yielding additional studies. Results: Deemed eligible was twenty-three systematic reviews and the databases included other than MEDLINE, EMBASE and CENTRAL was AMED, CINAHL, HealthSTAR, MANTIS, OT-Seeker, PEDro, PsychINFO, SCOPUS, SportDISCUS and Web of Science. Cumulative median recall for combined searching in MEDLINE, EMBASE and CENTRAL was 88.9% and increased to 90.9% when adding 10 additional databases. Conclusion: Searching MEDLINE, EMBASE and CENTRAL was not sufficient for identifying all effect studies on musculoskeletal disorders, but additional ten databases did only increase the median recall by 2%. It is possible that searching databases is not sufficient to identify all relevant references, and that reviewers must rely upon additional sources in their literature search. However further research is needed.