Background and objective: A large number of trials remain difficult to locate or unpublished for systematic reviews. The objective of this article was to determine the usefulness of making e-mail contact with authors of clinical trials and literature reviews found in MEDLINE to identify unpublished or difficult to locate Randomized Controlled Trials (RCTs).
Materials and methods: A structured search for detecting RCTs in MEDLINE was made from January 1999 to June 2003; a questionnaire was sent to a random sample of 525 author's mails. Those RCTs obtained were sought in MEDLINE, EMBASE, the Cochrane Controlled Trials Register, LILACS, and ongoing registers.
Results: 40 (7.6%) replies were received; 10 previously undescribed and unpublished RCTs and 21 unregistered ongoing RCTs were found. The most frequently given reasons for not publishing were: lack of time for finalizing the statistical analysis and preparing the manuscript, contractual obligations with the pharmaceutical industry, methodologic errors in designing, and editorial rejection.
Conclusions: Using the e-mails of authors detected by the search in electronic databases could contribute toward detecting potentially relevant ongoing or unpublished RCTs enabling rapid, straightforward, low-cost systematic review; in addition, the results of this study support the need of universal registration of all studies at their inception.