Objective To estimate the frequency with which results of large randomized clinical trials registered with ClinicalTrials.gov are not available to the public.
Design Cross sectional analysis
Setting Trials with at least 500 participants that were prospectively registered with ClinicalTrials.gov and completed prior to January 2009.
Data sources PubMed, Google Scholar, and Embase were searched to identify published manuscripts containing trial results. The final literature search occurred in November 2012. Registry entries for unpublished trials were reviewed to determine whether results for these studies were available in the ClinicalTrials.gov results database. Read more