title: Rates and determinants of informed consent: a case study of an international thromboprophylaxis trial.
abstract: BACKGROUND
  Successful completion of randomized trials depends upon efficiently and ethically screening patients and obtaining informed consent. Awareness of modifiable barriers to obtaining consent may inform ongoing and future trials.
  
  
  OBJECTIVE
  The objective of this study is to describe and examine determinants of consent rates in an international heparin thromboprophylaxis trial (Prophylaxis for ThromboEmbolism in Critical Care Trial, clinicaltrials.gov NCT00182143).
  
  
  METHODS
  Throughout the 4-year trial, research personnel approached eligible critically ill patients or their substitute decision makers for informed consent. Whether consent was obtained or declined was documented daily.
  
  
  METHODS
  The trial was conducted in 67 centers in 6 countries.
  
  
  RESULTS
  A total of 3764 patients were randomized. The overall consent rate was 82.2% (range, 50%-100%) across participating centers. Consent was obtained from substitute decision makers and patients in 90.1% and 9.9% of cases, respectively. Five factors were independently associated with consent rates. Research coordinators with more experience achieved higher consent rates (odds ratio [OR], 3.43; 95% confidence interval, 2.42-4.86; P < .001 for those with >10 years of experience). Consent rates were higher in smaller intensive care units with less than 15 beds compared with intensive care units with 15 to 20 beds, 21 to 25 beds, and greater than 25 beds (all ORs, <0.5; P < .001) and were higher in centers with more than 1 full-time research staff (OR, 1.95; 95% confidence interval, 1.28-2.99; P < .001). Consent rates were lower in centers affiliated with the Canadian Critical Care Trials Group or the Australian and New Zealand Intensive Care Society Clinical Trials Group compared with other centers (OR, 0.57; 95% confidence interval, 0.42-0.77; P < .001). Finally, consent rates were highest during the pilot trial, lowest during the initiation of the full trial, and increased over years of recruitment (P < .001).
  
  
  CONCLUSIONS
  Characteristics of study centers, research infrastructure, and experience were important factors associated with successfully procuring informed consent to participate in this thromboprophylaxis trial.
authors.affiliation: Interdepartmental Division of Critical Care, Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Orla M
authors.initials: OM
authors.lastname: Smith
authors.forename: Ellen
authors.initials: E
authors.lastname: McDonald
authors.forename: Nicole
authors.initials: N
authors.lastname: Zytaruk
authors.forename: Denise
authors.initials: D
authors.lastname: Foster
authors.forename: Andrea
authors.initials: A
authors.lastname: Matte
authors.forename: France
authors.initials: F
authors.lastname: Clarke
authors.forename: Laurie
authors.initials: L
authors.lastname: Meade
authors.forename: Nicole
authors.initials: N
authors.lastname: O'Callaghan
authors.forename: Shirley
authors.initials: S
authors.lastname: Vallance
authors.forename: Pauline
authors.initials: P
authors.lastname: Galt
authors.forename: Dorrilyn
authors.initials: D
authors.lastname: Rajbhandari
authors.forename: Marcelo
authors.initials: M
authors.lastname: Rocha
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Mehta
authors.forename: Niall D
authors.initials: ND
authors.lastname: Ferguson
authors.forename: Richard
authors.initials: R
authors.lastname: Hall
authors.forename: Robert
authors.initials: R
authors.lastname: Fowler
authors.forename: Karen
authors.initials: K
authors.lastname: Burns
authors.forename: Ismael
authors.initials: I
authors.lastname: Qushmaq
authors.forename: Marlies
authors.initials: M
authors.lastname: Ostermann
authors.forename: Diane
authors.initials: D
authors.lastname: Heels-Ansdell
authors.forename: Deborah
authors.initials: D
authors.lastname: Cook
mesh_terms: D019983:Guideline Adherence; D006801:Humans; D007258:Informed Consent / Q000941:ethics; D007362:Intensive Care Units; D016015:Logistic Models; D015999:Multivariate Analysis; D019982:Organizational Case Studies; D016032:Randomized Controlled Trials as Topic / Q000941:ethics; D013923:Thromboembolism / Q000517:prevention & control*; D035862:Vulnerable Populations