Association of time to colonoscopy after a positive fecal test result and fecal hemoglobin concentration with risk of advanced colorectal neoplasia

Background: We evaluated the risk of advanced colorectal neoplasia (ACRN) and colorectal cancer (CRC) according to time to colonoscopy after positive fecal immunochemical test (FIT), fecal hemoglobin concentration, and combination of both. Methods: We analyzed the records of 2362 patients aged ≥50 years who underwent colonoscopy because of a positive FIT result through the National Cancer Screening Program of Korea. Results: ACRN risk increased with increasing time to colonoscopy after a positive FIT (17.2%, 18.6%, 19.1%, 21.4%, and 27.2% in <30, 30–59, 60–149, 150–179, and ≥180 days; P = 0.034), and ACRN and CRC risk increased with increasing fecal hemoglobin concentration (ACRN, 13.2%, 16.9%, 18.5%, 23.2%, and 26.6%; CRC, 1.3%, 1.7%, 4.7%, 5.7%, and 12.8% with 100–200, 200–300, 300–500, 500–1000, and ≥1000 ng Hb/mL; both P < 0.001). Even after adjusting for confounders, follow-up after 180 days tended to be associated with a higher ACRN risk (adjusted odds ratio, 1.73; 95% confidence interval [CI], 0.91-3.27), compared with follow-up colonoscopy at <30 days, and fecal hemoglobin 500–1000, and ≥1000 ng Hb/mL were associated with a significantly higher ACRN and CRC risk, compared with 100–200 ng Hb/mL. Moreover, the group with ≥180 days and ≥1000 ng Hb/mL had a much higher CRC risk compared with the group with <180 days and <1000 ng Hb/mL (12.45-fold; 95% CI, 3.73–41.57). Conclusions: Patients with positive FIT results, especially those with higher fecal hemoglobin levels, should undergo timely follow-up colonoscopy.