Title | Should meta-analysts search Embase in addition to Medline? |
Publication Type | Journal Article |
Year of Publication | 2003 |
Authors | Sampson M, Barrowman NJ, Moher D, Klassen TP, Pham B', Platt R, St John PD, Viola R, Raina P |
Journal | Journal of clinical epidemiology |
Volume | 56 |
Issue | 10 |
Pagination | 943-55 |
Date Published | 2003 Oct |
ISSN | 0895-4356 |
Keywords | Databases, Bibliographic; Humans; MEDLINE; Meta-Analysis as Topic; Odds Ratio; Periodicals as Topic; Randomized Controlled Trials as Topic; Selection Bias |
Abstract | It is widely accepted that meta-analysts should search multiple databases. The selection of databases is ideally based on the potential contribution of each database to the project or on the potential for bias if a database is excluded, as supported by research evidence. We explore whether searching Embase yields additional trials that influence a meta-analysis. We identified meta-analyses that searched Medline and Embase. A random-effects weighted mean method was used to estimate the intervention effect in articles indexed only in Embase compared with those indexed elsewhere. On average, Embase-unique trials yielded significantly smaller estimates by 29% (ratio of odds ratio [ROR] 0.71, 95% confidence interval [CI] 0.56-0.90) but influenced the pooled estimate by an average of only 6% (ROR 0.94, 95% CI 0.88-0.99). Searching Medline but not Embase risks biasing a meta-analysis by finding studies that show larger estimates, but their prevalence seems low enough that the risk may be slight, provided the rest of the search is comprehensive. |
Alternate Journal | J Clin Epidemiol |