Sensitivity of immunochemical fecal occult blood test to small colorectal adenomas

BACKGROUND: Although the immunochemical fecal occult blood test (FOBT) is reportedly more sensitive to large adenomas or colorectal cancer (CRC) than the guaiac-based FOBT, the sensitivity of the immunochemical FOBT to small adenomas has scarcely been reported. Previous reports have indicated that the guaiac-based FOBT can detect small adenomas only by serendipity. OBJECTIVES: To investigate the sensitivity of immunochemical FOBT to small adenomas using a large-scale cohort. METHODS: We analyzed 21,805 consecutively enrolled asymptomatic persons who underwent colonoscopy and immunochemical FOBT. RESULTS: The sensitivity to adenomas <= 9 mm was significantly higher than the false-positive rate as revealed by analysis of all eligible subjects (7.0% vs 4.5%, P < 0.001). In men, the sensitivity was superior to the false-positive rate and increased with age (< 50 yr 6.1% and > 60 yr 11.3%). On the other hand, the sensitivity in women was not significantly different from the false-positive rate in any generation (5.1% vs 4.7% for all eligible women, P = 0.72). CONCLUSIONS: Immunochemical FOBT detected a small percentage of small adenomas in men at a rate that is significantly higher than the false-positive rate. Studies comparing the guaiac and immunochemical FOBTs using the end point of CRC-related death are expected.