Comparison of Availability of Trial Results in ClinicalTrials.gov and PubMed by Data Source and Funder Type.

This study examines the dissemination of trial results by data source (ie, ClinicalTrials.gov and PubMed) and funder type (ie, industry and nonindustry).

Publication of NIH funded trials registered in ClinicalTrials.gov: cross sectional analysis.

OBJECTIVE: To review patterns of publication of clinical trials funded by US National Institutes of Health (NIH) in peer reviewed biomedical journals indexed by Medline. DESIGN: Cross sectional analysis. SETTING: Clinical trials funded by NIH and registered within ClinicalTrials.gov (clinicaltrials.gov), a trial registry and results database maintained by the US National Library of Medicine, after 30 September 2005 and updated as having been completed by 31 December 2008, allowing at least 30 months for publication after completion of the trial. MAIN OUTCOME MEASURES: Publication and time to publication in the biomedical literature, as determined through Medline searches, the last of which was performed in June 2011. RESULTS: Among 635 clinical trials completed by 31 December 2008, 294 (46%) were published in a peer reviewed biomedical journal, indexed by Medline, within 30 months of trial completion. The median period of follow-up after trial completion was 51 months (25th-75th centiles 40-68 months), and 432 (68%) were published overall. Among published trials, the median time to publication was 23 months (14-36 months). Trials completed in either 2007 or 2008 were more likely to be published within 30 months of study completion compared with trials completed before 2007 (54% (196/366) v 36% (98/269); P<0.001). CONCLUSIONS: Despite recent improvement in timely publication, fewer than half of trials funded by NIH are published in a peer reviewed biomedical journal indexed by Medline within 30 months of trial completion. Moreover, after a median of 51 months after trial completion, a third of trials remained unpublished.

Trial Registration at ClinicalTrials.gov between May and October 2005.

BACKGROUND: Clinical trial registration allows interested parties to obtain information about ongoing and completed trials, but there are few data indicating the quality of the information provided during the registration process. We used information in the publicly available ClinicalTrials.gov database to describe patterns of trial registration before and after the implementation by journal editors of a new policy requiring registration as a prerequisite for publication. METHODS: We reviewed ClinicalTrials.gov records to determine patterns of completion of the "Intervention Name" and "Primary Outcome Measure" data fields for trials registered on May 20 and October 11, 2005, and for trials registered during the interval between these two dates, inclusively. RESULTS: During the interval studied, the number of registrations in ClinicalTrials.gov increased by 73 percent from 13,153 to 22,714. The percentage of interventional trials registered by industry with nonspecific Intervention Name entries (attributable to four drug companies) decreased from 10 percent to 2 percent; all other industry and nonindustry records contained specific entries in this field. Of the 2670 studies registered by industry between the two dates, 76 percent provided information in the Primary Outcome Measure field, although these entries varied markedly in their degree of specificity. In the remaining 24 percent of the records, this field was blank. CONCLUSIONS: During the summer of 2005, there were large increases in the number of clinical trial registrations. Overall, the data contained in records were more complete in October than they were in May, but there still is room for substantial improvement.