Database combinations to retrieve systematic reviews in Overviews of reviews: A methodological study

Abstract Background When conducting an Overviews of Reviews on health-related topics it is unclear which combination of bibliographic databases authors should use for searching for systematic reviews. Our goal was to determine which databases indexed the most systematic reviews and identify an optimal database combination for searching systematic reviews. Methods A set of 86 Overviews of Reviews with 1219 included systematic reviews was extracted from a previous study. Indexing of the systematic reviews was assessed in MEDLINE, CINAHL, DARE, Embase, Epistemonikos, PsycINFO, and TRIP. The mean indexing rate (% of indexed systematic reviews) and corresponding 95% confidence interval were calculated for each database individually, as well as for combinations of MEDLINE with other databases and reference checking. Results Indexing of systematic reviews was higher in MEDLINE than in any other single database (mean indexing rate 89.7%; 95% confidence interval [89.0–90.3%]). Combined with reference checking, this value increased to 93.7% [93.2–94.2%]. The best combination of two databases plus reference checking consisted of MEDLINE and Epistemonikos (99.2% [99.0–99.3%]). Stratification by Health Technology Assessment reports (97.7% [96.5–98.9%]) vs. Cochrane overviews (100.0%) vs. non-Cochrane overviews (99.3% [99.1–99.4%]) showed that indexing was only slightly lower for Health Technology Assessment reports. However, MEDLINE, Epistemonikos, and reference checking remained the best combination. Among the 10/1219 systematic reviews not identified by this combination, five were published as websites rather than journals, two were indexed in CINAHL and Embase, and one was indexed in the database ERIC. Conclusions MEDLINE/Epistemonikos, complemented by reference checking, is the best database combination to identify systematic reviews on health-related topics.