Diagnostic performance of colonoscopy after positive FIT in National Cancer Screening Program.

The National Cancer Screening Program of Korea provides an annual fecal immunochemical test (FIT) for adults aged ≥50 years. We evaluated the diagnostic performance of colonoscopy and the prevalence ratio (PR) of advanced neoplasia (AN) in participants with positive FIT results under the National Cancer Screening Program between 2007 and 2024. The PR of AN was compared between binary groups created based on age, sex, waiting time to colonoscopy, FIT cutoff value, and anemia. Among the 2445 participants with positive FIT results, 1237 (50.6%) underwent colonoscopy. The positive predictive values for non-AN, AN, and sessile serrated lesions were 31.2%, 15.4%, and 14.6%, respectively. The PR of AN was 1.8 times higher in males than in females (P < .001) and 1.9 times higher in the standard FIT cutoff group than in the low FIT cutoff group (P < .001). In the multivariable analysis, male sex (PR = 1.84, 95% confidence interval: 1.36-2.50) and FIT positivity based on the standard cutoff (PR = 1.86, 95% confidence interval: 1.33-2.61) were significantly associated with AN (both P < .001). ANs were more frequently detected in male participants and when the standard FIT cutoff value was used in FIT-based colorectal cancer screening. Given the low colonoscopy completion rate of only 50.6%, colonoscopy completion should be recommended, particularly for male participants and those with positive FIT results based on the standard cutoff value.