Ross, JS; Mulvey, GK; Hines, EM; Nissen, SE; Krumholz, HM
Background: ClinicalTrials.gov is a publicly accessible,
Internet-based registry of clinical trials managed by the US National Library of Medicine that
has the potential to address selective trial publication. Our objectives were to examine
completeness of registration within ClinicalTrials.gov and to determine the extent and correlates
of selective publication. Methods and Findings: We examined reporting of registration information
among a cross-section of trials that had been registered at ClinicalTrials.gov after December 31,
1999 and updated as having been completed by June 8, 2007, excluding phase I trials. We then
determined publication status among a random 10% subsample by searching MEDLINE using a
systematic protocol, after excluding trials completed after December 31, 2005 to allow at least 2
y for publication following completion. Among the full sample of completed trials (n= 7,515),
nearly 100% reported all data elements mandated by ClinicalTrials.gov, such as intervention and
sponsorship. Optional data element reporting varied, with 53% reporting trial end date, 66%
reporting primary outcome, and 87% reporting trial start date. Among the 10% subsample, less than
half (311 of 677, 46%) of trials were published, among which 96 (31%) provided a citation within
ClinicalTrials.gov of a publication describing trial results. Trials primarily sponsored by
industry (40%, 144 of 357) were less likely to be published when compared with
nonindustry/nongovernment sponsored trials (56%, 110 of 198; p < 0.001), but there was no
significant difference when compared with government sponsored trials (47%, 57 of 122; p = 0.22).
Among trials that reported an end date, 75 of 123 (61%) completed prior to 2004, 50 of 96 (52%)
completed during 2004, and 62 of 149 (42%) completed during 2005 were published (p = 0.006).
Conclusions: Reporting of optional data elements varied and publication rates among completed
trials registered within ClinicalTrials.gov were low. Without greater attention to reporting of
all data elements, the potential for ClinicalTrials.gov to address selective publication of
clinical trials will be limited.