title: Predictors of colorectal cancer following a negative colonoscopy in the Medicare population.
abstract: BACKGROUND
  The incidence of colorectal cancer following a normal colonoscopy in the Medicare population is not known.
  
  
  METHODS
  A 5% national sample of Medicare enrollees from 1996 to 2005 was used to identify patients undergoing complete colonoscopy. A colonoscopy not associated with any procedure (e.g., biopsy, polypectomy or fulguration) was defined as a negative colonoscopy. Patients with history of inflammatory bowel disease, colorectal cancer or death within 12 months of colonoscopy were excluded. A multivariable model was constructed to evaluate the factors associated with a new diagnosis of colorectal cancer in the period from 12 to 120 months following the negative colonoscopy.
  
  
  RESULTS
  Among 200,857 patients (mean age 74 years, 61% female, 92% White) with a negative colonoscopy, the incidence of colorectal cancer was 1.8 per 1,000 person-years. The incidence rate for matched follow-up periods decreased from 2.0/1,000 person-years for patients undergoing colonoscopy during 1996-2000 to 1.2/1,000 person years during 2001-2005. Multivariate analysis revealed a significant regional variation in the incidence of colorectal cancer following a negative colonoscopy. The incidence was higher in patients >85 years, males and patients who underwent a negative colonoscopy by a non-gastroenterologist or endoscopist in the lowest volume quartile. On stratified analyses, endoscopist volume was a significant predictor for non-gastroenterologists only.
  
  
  CONCLUSIONS
  The specialty and experience of the endoscopist are significant predictors of the incidence rate of colorectal cancer in Medicare patients with a negative colonoscopy.
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, University of Texas Medical Branch (UTMB), 301 University Blvd., Galveston, TX 77555-0764, USA. amasingh@utmb.edu
authors.forename: Amanpal
authors.initials: A
authors.lastname: Singh
authors.forename: Yong-Fang
authors.initials: YF
authors.lastname: Kuo
authors.forename: Taylor S
authors.initials: TS
authors.lastname: Riall
authors.forename: G S
authors.initials: GS
authors.lastname: Raju
authors.forename: James S
authors.initials: JS
authors.lastname: Goodwin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D006278:Medicare; D014481:United States