Identifying systematic reviews of the adverse effects of health care interventions

BACKGROUND In order to carry out a methodological research survey of systematic reviews of adverse effects we needed to retrieve a sample of systematic reviews in which the primary outcome is an adverse effect or effects. METHODS We carried out searches of the Database of Abstracts of Reviews of Effects (DARE) and the Cochrane Database of Systematic Reviews (CDSR) for systematic reviews of adverse effects published between 1994 to 2005. The search strategies used a combination of text words in the title and abstract, Medical Subject Headings (MeSH) and subheadings/qualifiers. In addition, DARE records in progress were hand searched. No language restrictions were placed on any of the searches. The performance, in terms of sensitivity and precision, of the search strategies and their combinations were tested in DARE and CDSR. RESULTS In total 3635 records were screened of which 257 met our inclusion criteria. The precision of the searches in CDSR was low (0% to 3%), and no one search strategy could retrieve all the relevant records in either DARE or CDSR. Hand searching the records from DARE and CDSR not retrieved by our searches indicated that we had missed relevant systematic reviews in both DARE and CDSR. The sensitivities of many of the search combinations were comparable to those found when searching for primary studies in which adverse effects are secondary outcomes. CONCLUSION Searching major databases of systematic reviews, for systematic reviews of adverse effects, proved more difficult than anticipated due to a lack of standard terminology used by the authors, inadequate indexing and the variations in the search interfaces of the databases. At present hand searching all records in DARE and CDSR seems to be the only way to ensure retrieval of all systematic reviews of adverse effects in these databases.