title: Characteristics of clinical trials registered in ClinicalTrials.gov, 2007-2010.
abstract: BACKGROUND
  Recent reports highlight gaps between guidelines-based treatment recommendations and evidence from clinical trials that supports those recommendations. Strengthened reporting requirements for studies registered with ClinicalTrials.gov enable a comprehensive evaluation of the national trials portfolio.
  
  
  OBJECTIVE
  To examine fundamental characteristics of interventional clinical trials registered in the ClinicalTrials.gov database.
  
  
  METHODS
  A data set comprising 96,346 clinical studies from ClinicalTrials.gov was downloaded on September 27, 2010, and entered into a relational database to analyze aggregate data. Interventional trials were identified and analyses were focused on 3 clinical specialties-cardiovascular, mental health, and oncology-that together encompass the largest number of disability-adjusted life-years lost in the United States.
  
  
  METHODS
  Characteristics of registered clinical trials as reported data elements in the trial registry; how those characteristics have changed over time; differences in characteristics as a function of clinical specialty; and factors associated with use of randomization, blinding, and data monitoring committees (DMCs).
  
  
  RESULTS
  The number of registered interventional clinical trials increased from 28,881 (October 2004-September 2007) to 40,970 (October 2007-September 2010), and the number of missing data elements has generally declined. Most interventional trials registered between 2007 and 2010 were small, with 62% enrolling 100 or fewer participants. Many clinical trials were single-center (66%; 24,788/37,520) and funded by organizations other than industry or the National Institutes of Health (NIH) (47%; 17,592/37,520). Heterogeneity in the reported methods by clinical specialty; sponsor type; and the reported use of DMCs, randomization, and blinding was evident. For example, reported use of DMCs was less common in industry-sponsored vs NIH-sponsored trials (adjusted odds ratio [OR], 0.11; 95% CI, 0.09-0.14), earlier-phase vs phase 3 trials (adjusted OR, 0.83; 95% CI, 0.76-0.91), and mental health trials vs those in the other 2 specialties. In similar comparisons, randomization and blinding were less frequently reported in earlier-phase, oncology, and device trials.
  
  
  CONCLUSIONS
  Clinical trials registered in ClinicalTrials.gov are dominated by small trials and contain significant heterogeneity in methodological approaches, including reported use of randomization, blinding, and DMCs.
authors.affiliation: Duke Translational Medicine Institute, 200 Trent Dr, 1117 Davison Bldg, Durham, NC 27710, USA. robert.califf@duke.edu
authors.forename: Robert M
authors.initials: RM
authors.lastname: Califf
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Zarin
authors.forename: Judith M
authors.initials: JM
authors.lastname: Kramer
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Sherman
authors.forename: Laura H
authors.initials: LH
authors.lastname: Aberle
authors.forename: Asba
authors.initials: A
authors.lastname: Tasneem
mesh_terms: D002318:Cardiovascular Diseases / Q000628:therapy; D002986:Clinical Trials as Topic / Q000592:standards* / Q000706:statistics & numerical data*; D016208:Databases, Factual; D004345:Drug Industry; D006801:Humans; D001523:Mental Disorders / Q000628:therapy; D009316:National Institutes of Health (U.S.); D009369:Neoplasms / Q000628:therapy; D016032:Randomized Controlled Trials as Topic; D012042:Registries / Q000706:statistics & numerical data*; D012107:Research Design; D012109:Research Support as Topic; D018401:Sample Size; D014481:United States