Sigmoidoscopy Screening: Understanding the Trade-off Between Detection of Advanced Neoplasia and Diagnostic Efficiency

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colonoscopy vs biennial fecal immunochemical testing (FIT) (10) to compare the three sets of criteria for colonoscopy referral. The criteria sets were compared in asymptomatic persons aged 50–69 years who were either randomly assigned to the colonoscopy arm of the trial or who were randomly assigned to and eligible for the FIT arm but requested a screening colonoscopy instead. The end points for comparison were 1) detection rate for any advanced neoplasia; 2) test characteristics for APN; and 3) number needed to screen to detect one person with APN. All estimates were based on simulation of sigmoidoscopy from colonoscopic findings. Two definitions of distal were considered—one with and one without the descending colon. Test characteristics were measured in age- and sex-specific subgroups. Distal findings were explored as predictors of APN (9). Colonoscopy referral would have occurred for 6.2% of the study population using the UK criteria, 12.0% using the SCORE criteria, and 17.9% using the NORCCAP criteria. NORCCAP criteria were most sensitive for APN whereas UK criteria were most specific and efficient. Colonoscopy detected any advanced neoplasia in 520 of 5059 (10.3%) individuals, whereas detection with the three sets of criteria ranged from 6.3% for the UK criteria to 7.0% for NORCCAP, which is 61% to 68% of all advanced neoplasia. Colonoscopy identified APN in 255 (5.0%) persons. Sensitivity of the referral criteria for APN ranged from 22% for the UK criteria to 37% for NORCCAP. Among persons referred, the number needed to screen with colonoscopy to detect one person with APN was six for the U.K. criteria, eight for SCORE, and 10 for NORCCAP. Including the descending colon with the distal colon improved APN sensitivity by absolute amounts of 2% to 4% overall, by 5% to 8% for men aged 50–59 years, and by 8% to 9% for women aged 60–69 years. A large (≥10 mm) distal adenoma was the strongest independent predictor of APN.