Context Recent reports
highlight gaps between guidelines-based treatment recommendations and
evidence from clinical trials that supports
those recommendations. Strengthened reporting
requirements for studies registered with ClinicalTrials.gov enable a
evaluation of the national trials portfolio.
Objective To examine fundamental characteristics of interventional clinical trials registered in the ClinicalTrials.gov database.
Methods A data set
comprising 96 346 clinical studies from ClinicalTrials.gov was
downloaded on September 27, 2010, and entered into
a relational database to analyze aggregate data.
Interventional trials were identified and analyses were focused on 3
specialtiescardiovascular, mental health, and
oncologythat together encompass the largest number of
life-years lost in the United States.
Main Outcome Measures
Characteristics of registered clinical trials as reported data elements
in the trial registry; how those characteristics
have changed over time; differences in
characteristics as a function of clinical specialty; and factors
associated with use
of randomization, blinding, and data monitoring
Results The number of
registered interventional clinical trials increased from 28 881 (October
2004September 2007) to 40 970 (October
2007September 2010), and the number of missing
data elements has generally declined. Most interventional trials
between 2007 and 2010 were small, with 62%
enrolling 100 or fewer participants. Many clinical trials were
24 788/37 520) and funded by organizations other
than industry or the National Institutes of Health (NIH) (47%;
17 592/37 520).
Heterogeneity in the reported methods by clinical
specialty; sponsor type; and the reported use of DMCs, randomization,
blinding was evident. For example, reported use of
DMCs was less common in industry-sponsored vs NIH-sponsored trials
odds ratio [OR], 0.11; 95% CI, 0.09-0.14),
earlier-phase vs phase 3 trials (adjusted OR, 0.83; 95% CI, 0.76-0.91),
health trials vs those in the other 2 specialties.
In similar comparisons, randomization and blinding were less frequently
reported in earlier-phase, oncology, and device
trials registered in ClinicalTrials.gov are dominated by small trials
and contain significant heterogeneity in methodological
approaches, including reported use of
randomization, blinding, and DMCs.