title: Registration practices for observational studies on ClinicalTrials.gov indicated low adherence.
abstract: OBJECTIVE
  The study aims to assess the status of registration of observational studies.
  
  
  METHODS
  We identified studies on cancer research with prospective recruitment of participants that were registered from February 2000 to December 2011 in ClinicalTrials.gov. We recorded the dates of registration and start of recruitment, outcomes, and description of statistical method. We searched for publications corresponding to the registered studies through May 31, 2014.
  
  
  RESULTS
  One thousand one hundred nine registered studies were eligible. Primary and secondary outcomes were reported in 809 (73.0%) and 464 (41.8%) of them. The date of registration preceded the month of the study start in 145 (13.8%) and coincided in 205 (19.5%). A total of 151 publications from 120 (10.8%) registered studies were identified. In 2 (33.3%) of the 6 publications where ClinicalTrials.gov reported that the study started recruitment after registration, and in 9 (50.0%) of 18 publications where ClinicalTrials.gov reported the same date for registration and start of recruitment, the articles showed that the study had actually started recruiting before registration.
  
  
  CONCLUSIONS
  During the period reviewed, few observational studies have been registered. Registration usually occurred after the study started, and prespecification of outcomes and statistical analysis rarely occurred.
authors.affiliation: Section of Hygiene, Institute of Public Health, Università Cattolica del Sacro Cuore, L.go F. Vito, 1, Rome 00168, Italy. Electronic address: sboccia@rm.unicatt.it.
authors.forename: Stefania
authors.initials: S
authors.lastname: Boccia
authors.affiliation: RTI Health Solutions, Research Triangle Institute, Research Triangle Park, NC, USA; Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
authors.affiliation: Section of Hygiene, Institute of Public Health, Università Cattolica del Sacro Cuore, L.go F. Vito, 1, Rome 00168, Italy.
authors.forename: Nikola
authors.initials: N
authors.lastname: Panic
authors.affiliation: Department of Medicine and Aging Sciences, University of Chieti, Via dei Vestini 5, 66013 Chieti, Italy; ASL Pescara, Via Renato Paolini 47, Pescara 65123, Italy.
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Flacco
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Rosso
authors.affiliation: Section of Hygiene, Institute of Public Health, Università Cattolica del Sacro Cuore, L.go F. Vito, 1, Rome 00168, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Pastorino
authors.affiliation: Department of Medicine and Aging Sciences, University of Chieti, Via dei Vestini 5, 66013 Chieti, Italy; CeSI Biotech, Via Colle dell'Ara, Chieti 66100, Italy.
authors.forename: Lamberto
authors.initials: L
authors.lastname: Manzoli
authors.affiliation: Department of Clinical Sciences and Community Health, University of Milan, Via Vanzetti 5, 20133, Milan, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: La Vecchia
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Villari
authors.affiliation: Population Sciences, Tisch Cancer Center and Institute for Translational Epidemiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
authors.forename: Paolo
authors.initials: P
authors.lastname: Boffetta
authors.affiliation: Section of Hygiene, Institute of Public Health, Università Cattolica del Sacro Cuore, L.go F. Vito, 1, Rome 00168, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Ricciardi
authors.affiliation: Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA; Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, USA; Department of Statistics, Stanford University School of Humanities and Sciences, Stanford, CA, USA; Meta-Research Innovation Center at Stanford (METRICS), Stanford University, Stanford, CA, USA.
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D006801:Humans; D009369:Neoplasms; D064887:Observational Studies as Topic; D010043:Outcome and Process Assessment, Health Care; D018579:Patient Selection; D011446:Prospective Studies; D017594:Publication Bias; D011643:Publishing; D013223:Statistics as Topic; D014481:United States
keywords: Cancer protocol registration; ClinicalTrials.gov; Outcome reporting bias; Protocol registration; Registration of observational studies; Registration study records