Clinical trial design and dissemination: comprehensive analysis of clinicaltrials.gov and PubMed data since 2005

Abstract

<h3>Abstract</h3> <h3>Objective</h3> To investigate the distribution, design characteristics, and dissemination of clinical trials by funding organisation and medical specialty. <h3>Design</h3> Cross sectional descriptive analysis. <h3>Data sources</h3> Trial protocol information from clinicaltrials.gov, metadata of journal articles in which trial results were published (PubMed), and quality metrics of associated journals from SCImago Journal and Country Rank database. <h3>Selection criteria</h3> All 45 620 clinical trials evaluating small molecule therapeutics, biological drugs, adjuvants, and vaccines, completed after January 2006 and before July 2015, including randomised controlled trials and non-randomised studies across all clinical phases. <h3>Results</h3> Industry was more likely than non-profit funders to fund large international randomised controlled trials, although methodological differences have been decreasing with time. Among 27 835 completed efficacy trials (phase II-IV), 15 084 (54.2%) had disclosed their findings publicly. Industry was more likely than non-profit trial funders to disseminate trial results (59.3% (10 444/17 627) <i>v</i> 45.3% (4555/10 066)), and large drug companies had higher disclosure rates than small ones (66.7% (7681/11 508) <i>v</i> 45.2% (2763/6119)). Trials funded by the National Institutes of Health (NIH) were disseminated more often than those of other non-profit institutions (60.0% (1451/2417) <i>v</i> 40.6% (3104/7649)). Results of studies funded by large drug companies and NIH were more likely to appear on clinicaltrials.gov than were those from non-profit funders, which were published mainly as journal articles. Trials reporting the use of randomisation were more likely than non-randomised studies to be published in a journal article (6895/19 711 (34.9%) <i>v</i> 1408/7748 (18.2%)), and journal publication rates varied across disease areas, ranging from 42% for autoimmune diseases to 20% for oncology. <h3>Conclusions</h3> Trial design and dissemination of results vary substantially depending on the type and size of funding institution as well as the disease area under study.