The comprehensiveness of Medline and Embase computer searches. Searches for controlled trials of homoeopathy, ascorbic acid for common cold and ginkgo biloba for cerebral insufficiency and intermittent claudication.

Objective: To assess the comprehensiveness of Medline and Embase computer searches for controlled trials.

Design: Comparison of articles found after an exhaustive search of the literature with the yield of a Medline or Embase search. This was performed for controlled clinical trials on the efficacy of three interventions: homoeopathy, ascorbic acid for common cold, and ginkgo biloba for intermittent claudication and cerebral insufficiency. The number of controlled trials found by exhaustive search of the literature was 107, 61 and 45, respectively.

Results: For homoeopathy, ascorbic acid and ginkgo the proportion of all trials found by Medline was 17%, 36% and 31% respectively and for Embase 13%, 25% and 58% respectively. After checking of the references in the Medline articles 44%, 79% and 76% of all trials were identified. After checking of the references in the Embase articles 42%, 72% and 93% of all trials were identified. About 20% of the articles was not correctly indexed. Of the best trials 68%, 91% and 83% could be found with Medline and 55%, 82% and 92% of the best trials were identified through Embase.

Conclusions: For the topics mentioned, Medline and Embase searches are sufficient to get an impression of the evidence from controlled trials, but only if references in the articles are followed for further evidence. If one wants to get a more complete picture, additional search strategies make sense. Of course, this picture may be different for other topics.