Trial Registration at ClinicalTrials.gov between May and October 2005

Abstract

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.

Figure 1. Categories of Trials Registered in ClinicalTrials.gov on or between May 20 and October 11, 2005

Panel A shows the origins and types of trials registered in ClinicalTrials.gov on or between May 20 and October 11, 2005. Trials were categorized as observational or interventional. Study 1 focused on the interventional trials (shaded). Trials were registered by the National Institutes of Health and other U.S. federal agencies, industry, and universities, foundations, and other organizations (denoted “University”). “Interval” denotes the period between May 20 and October 11. Panel B shows interventional trials registered in ClinicalTrials.gov on or between May 20 and October 11, 2005, according to whether they included at least one drug or vaccine intervention (if so, they are denoted “drug trials”). Study 2, which assessed the use of the Intervention Name field, focused on the trials that included a drug or vaccine (shaded). Panel C shows interventional trials registered in ClinicalTrials.gov on or between May 20 and October 11, 2005, according to whether they were registered by industry (denoted “industry”) or by other data providers (denoted “nonindustry”). Study 3, which assessed the use of the Primary Outcome Measure field, included only the trials that were registered by industry during the interval period (shaded).

Figure 2. New Trials Registered in ClinicalTrials.gov, According to Week

The figure shows the number of new registrations per week (beginning on the date indicated) from mid-May through early October 2005. The “Industry” category includes all commercial data providers; the “Federal” category includes the National Institutes of Health and other U.S. federal data providers; and the “University” category includes universities, foundations, and other providers.