Transparency in the release of human subjects trials results in the public domain among studies registered on clinicaltrials.gov

The information on clinical trials should be accessed by the public to maintain transparency. ClinicalTrials.gov (CTG) is a national web-based resource where clinical trials are registered and some of them are required to submit the results under the Food and Drug Administration Amendments Act of 2007. In this study, the CTG data set of registered trials was analyzed to identify predictors of transparency vs. non-transparency. We defined ‘transparency' as either posting results on CTG or publishing the main effects article, and ‘non-transparency' as neither posting results on CTG nor publishing the main effects article. We conducted univariate, bivariate and logistic regression analyses. Among 1499 eligible interventional clinical trials registered on CTG and reported as completed in 2008 in CTG, 400 clinical trials were randomly selected. 118 clinical trials (29.5%) lacked transparency. Phase 2 clinical trials were more likely to be non-transparent than phase 3/4 clinical trials (adjusted OR 1.56; 95%CI 0.93 - 2.57, p=0.09); clinical trials run by industry-only were more likely to be non-transparent than clinical trials run by others (adjusted OR 1.7; 95%CI 0.92 – 3.18, p=0.09); and randomized control trials were more likely to be non-transparent than non-randomized clinical trials (adjusted OR 2.42; 95%CI 1.31 – 4.46, p=0.005). In conclusion, lack of transparency is common-place among trials registered on CTG, even with four years of time in which to release results into the public domain. Lack of transparency is more common among industry sponsored trials and those at earlier stages of clinical development.