title: Risk stratification for colon neoplasia: screening strategies using colonoscopy and computerized tomographic colonography.
abstract: OBJECTIVE
  We developed a risk index to identify low-risk patients who may be screened for colorectal cancer with computerized tomographic colonography (CTC) instead of colonoscopy.
  
  
  METHODS
  Asymptomatic persons aged 50 years or older who had undergone screening colonoscopy were randomized retrospectively to derivation (n = 1512) and validation (n = 1493) subgroups. We developed a risk index (based on age, sex, and family history) from the derivation group. The expected results of 3 screening strategies--universal colonoscopy, universal CTC, and a stratified strategy of colonoscopy for high-risk and CTC for low-risk patients--were then compared. Outcomes for the 3 strategies were extrapolated from the known colonic findings in each patient, using sensitivity/specificity values for CTC from the medical literature. Results were validated in the validation subgroup.
  
  
  RESULTS
  In the derivation subgroup, universal colonoscopy detected 94% of advanced neoplasia and universal CTC detected only 70% and resulted in the largest total number of procedures and number of patients undergoing both procedures. The stratified strategy detected 92% of advanced neoplasia, requiring colonoscopy in 68% and CTC in 36% of patients, with only 4% having to undergo both procedures. In the validation subgroup, universal colonoscopy detected 94% and universal CTC detected 71% of advanced neoplasia, whereas the stratified strategy detected 89%, requiring colonoscopy in 64% and CTC in 40%. Unlike universal CTC, the stratified strategy was independent of assumptions for CTC sensitivity, specificity, and threshold for colonoscopy.
  
  
  CONCLUSIONS
  The stratified strategy based on our risk index may optimize the yield of colonoscopic resources and reduce the number of patients undergoing colonoscopy.
authors.affiliation: Gastroenterology Section, Virginia Mason Medical Center, 1100 Ninth Avenue, Seattle, WA 98101, USA. Otto.Lin@vmmc.org
authors.forename: Otto S
authors.initials: OS
authors.lastname: Lin
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kozarek
authors.forename: Drew B
authors.initials: DB
authors.lastname: Schembre
authors.forename: Kamran
authors.initials: K
authors.lastname: Ayub
authors.forename: Michael
authors.initials: M
authors.lastname: Gluck
authors.forename: Nico
authors.initials: N
authors.lastname: Cantone
authors.forename: Maw-Soan
authors.initials: MS
authors.lastname: Soon
authors.forename: Jason A
authors.initials: JA
authors.lastname: Dominitz
mesh_terms: D003110:Colonic Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D003111:Colonic Polyps / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology; D023881:Colonography, Computed Tomographic / Q000191:economics / Q000592:standards / Q000706:statistics & numerical data*; D003113:Colonoscopy / Q000191:economics / Q000592:standards / Q000706:statistics & numerical data*; D005260:Female; D017048:Health Care Costs; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000191:economics / Q000379:methods / Q000592:standards; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity