Sponsorship and Design Characteristics of Trials Registered in ClinicalTrials.gov

Objective: We examine the extent to which ClinicalTrials.gov is meeting its goal of providing oversight and transparency of clinical trials with human subjects. We analyzed the ClinicalTrials.gov database contents as of June 2011, comparing interventions, medical conditions, and trial characteristics by sponsor type. We also conducted a detailed analysis of incomplete data.

Results: Among trials with only government sponsorship (N=9252), 36% were observational and 64% interventional; in contrast, almost all (90%) industry-only sponsored trials were interventional. Industry-only sponsored interventional trials (N=30,036) were most likely to report a drug intervention (81%), followed by biologics (9%) and devices (8%). Government-only interventional trials (N=5886) were significantly more likely to test behavioral interventions (28%) and procedures (13%) than industry-only trials (p<0.001). Medical conditions most frequently studied in industry-only trials were cancer (19%), cardiovascular conditions (12%) and endocrine/metabolic disorders (11%). Government-only funded trials were more likely to study mental health (19% vs. 7% for industry, p<.001), and viral infections, including HIV (15% vs 7% for industry, p<.001). Government-funded studies are significantly more likely to be missing data about study design and intervention arms in the registry. For all studies, we report ambiguous and contradictory data entries.

Conclusions: Industry-sponsored studies differ systematically from government-sponsored studies in study type, choice of interventions, conditions studied, and completeness of submitted information. Imprecise study design information, incomplete coding of conditions, out-of-date or unspecified enrollment numbers, and other missing data continue to hinder robust analyses of trials registered in ClinicalTrials.gov.