SYSTEMATIC REVIEWS - IDENTIFYING RELEVANT STUDIES FOR SYSTEMATIC REVIEWS

Objective-To examine the sensitivity and precision of Medline searchin g for randomised clinical trials. Design-Comparison of results of Medl ine searches to a ''gold standard'' of known randomised clinical trial s in ophthalmology published in 1988; systematic review (meta-analysis ) of results of similar, but separate, studies from many fields of med icine. Populations-Randomised clinical trials published in 1988 in jou rnals indexed in Medline, and those not indexed in Medline and identif ied by hand search, comprised the gold standard. Gold standards for th e other studies combined in the meta-analysis were based on: randomise d clinical trials published in any journal, whether indexed in Medline or not; those published in any journal indexed in Medline; or those p ublished in a selected group of journals indexed in Medline. Main outc ome measure-Sensitivity (proportion of the total number of known rando mised clinical trials identified by the search) and precision (proport ion of publications retrieved by Medline that were actually randomised clinical trials) were calculated for each study and combined to obtai n weighted means. Searches producing the ''best'' sensitivity were use d for sensitivity and precision estimates when multiple searches were performed. Results-The sensitivity of searching for ophthalmology rand omised clinical trials published in 1988 was 82%, when the gold standa rd was for any journal, 87% for any journal indexed in Medline, and 88 % for selected journals indexed in Medline. Weighted means for sensiti vity across all studies were 51%, 77%, and 63%, respectively. The weig hted mean for precision was 8% (median 32.5%). Most searchers seemed n ot to use freetext subject terms and truncation of those terms. Conclu sion-Although the indexing terms available for searching Medline for r andomised clinical trials have improved, sensitivity still remains uns atisfactory. A mechanism is needed to ''register'' known trials, prefe rably by retrospective tagging of Medline entries, and incorporating t rials published before 1966 and in journals not indexed by Medline int o the system.