title: Repeat colonoscopy after a colonoscopy with a negative result in Ontario: a population-based cohort study.
abstract: BACKGROUND
  Data suggest the overuse of repeat colonoscopies, especially in patients at low risk for colorectal cancer. Our objective was to evaluate the time to repeat colonoscopies in low-risk patients aged 50-79 years old and the associated patient- and endoscopist-related factors.
  
  
  METHODS
  All patients aged 50-79 years of age who underwent a complete outpatient colonoscopy with a negative result between 2000 and 2007 were identified from the Ontario Health Insurance Plan database. A colonoscopy performed within 5.5 years of follow-up after the index colonoscopy was considered an early repeat colonoscopy. Patient, endoscopist and endoscopy setting characteristics were recorded and their association with an early repeat colonoscopy was determined using an extended Cox proportional hazards regression model.
  
  
  RESULTS
  The cohort consisted of 546 467 patients: 55.4% of the patients were female with a mean age of 61.1 years (95% confidence interval [CI] 61.1-61.2). The cumulative percentage of early repeat colonoscopy after 5.5 years was 33.7%. The rate decreased significantly between 2000 and 2007 (hazard ratio [HR] 0.35, 95% CI 0.34-0.36). General surgeons were associated with a higher risk of early repeat colonoscopy than gastroenterologists (HR 1.27, 95% CI 1.25-1.28). Endoscopists practising in a nonhospital setting were more likely to perform an early repeat colonoscopy (HR 1.26, 95% CI 1.22-1.30) than endoscopists at a hospital.
  
  
  CONCLUSIONS
  This study showed that there was overuse of early repeat colonoscopy in more than 30% of patients who were at low risk for colorectal cancer. The risk decreased significantly between 2000 and 2007 but was still greater than 20% in 2007. Our findings can be used to develop targeted educational interventions among subgroups of endoscopists with a higher rate of early repeat colonoscopy.
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Department of Gastroenterology and Hepatology, Erasmus University Medical Centre, Rotterdam, the Netherlands.
authors.forename: Lieke
authors.initials: L
authors.lastname: Hol
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Dalla Lana School of Public Health, University of Toronto, Toronto, Ont.
authors.forename: Rinku
authors.initials: R
authors.lastname: Sutradhar
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Dalla Lana School of Public Health, University of Toronto, Toronto, Ont.
authors.forename: Sumei
authors.initials: S
authors.lastname: Gu
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Department of Surgery and Li Ka Shing Research Institute, St. Michael's Hospital, Toronto, Ont.
authors.forename: Nancy N
authors.initials: NN
authors.lastname: Baxter
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Prevention and Cancer Control, Cancer Care Ontario, Toronto, Ont.
authors.forename: Linda
authors.initials: L
authors.lastname: Rabeneck
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: Jill M
authors.initials: JM
authors.lastname: Tinmouth
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ont. ; Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Paszat