Reporting of results of interventional studies by the information service of the National Institutes of Health.

The Food and Drug Administration Amendments Act of 2007 mandated that sponsors of applicable studies must provide results within one year of study completion. We aimed to analyze the factors associated with reporting of results from interventional studies registered on ClinicalTrials.gov. On May 20, 2010, we retrieved 20 available fields from 57,233 closed studies on the website and identified 31,161 interventional studies that were required to post results. We compared the proportion of studies with results versus studies without results by age, gender, and disease status of participants, by interventions, sponsors, phase of clinical trials, and completion dates. The results of studies were reported for 4.7% of applicable studies, 8% of industry-sponsored studies, 7.5% of Phase II and 6.5% of Phase IV clinical trials, 4.9% of drug studies, and 0% of genetic studies. Withdrawn (n = 486) and suspended (n = 414) interventions did not provide results. The percentage of studies with results varied from 0% to 21% among different sponsors. The first studies with results were completed in 1992. The proportion of studies with results increased over time. Completion dates were not available for 7446 studies. The database does not have fields available to facilitate routine analysis of the rate of compliance with federal law for posting results. The analysis of accuracy of the protocols in relation to the results and publications is not possible without time-consuming evaluation of individual postings and individual publications.