How to identify randomized controlled trials in MEDLINE: ten years on

The researchers sought to assess whether the widely used 1994 Cochrane Highly Sensitive Search Strategy (HSSS) for randomized controlled trials (RCTs) in MEDLINE could be improved in terms of sensitivity, precision, or parsimony.

A gold standard of 1,347 RCT records and a comparison group of 2,400 non-trials were randomly selected from MEDLINE. Terms occurring in at least 1% of RCT records were identified. Fifty percent of the RCT and comparison group records were randomly selected, and the ability of the terms to discriminate RCTs from non-trial records was determined using logistic regression. The best performing combinations of terms were tested on the remaining records and in MEDLINE.

The best discriminating term was "Clinical Trial" (Publication Type). In years where the Cochrane assessment of MEDLINE records had taken place, the strategies identified few additional unindexed records of trials. In years where Cochrane assessment has yet to take place, "Randomized Controlled Trial" (Publication Type) proved highly sensitive and precise. Adding six more search terms identified further, unindexed trials at reasonable levels of precision and with sensitivity almost equal to the Cochrane HSSS.

Most reports of RCTs in MEDLINE can now be identified easily using "Randomized Controlled Trial" (Publication Type). More sensitive searches can be achieved by a brief strategy, the Centre for Reviews and Dissemination/Cochrane Highly Sensitive Search Strategy (2005 revision).