Effects of Oral Anticoagulants and Aspirin on Performance of Fecal Immunochemical Tests in Colorectal Cancer Screening

BACKGROUND & AIMS: The fecal immunochemical test (FIT) is the tool most frequently used for colorectal cancer (CRC) screening worldwide. It is unclear how the use of aspirin and oral anticoagulants in the screening population affects the diagnostic performance of FIT. METHODS: We performed a cross-sectional study in an ongoing CRC screening trial in Norway. Participants aged 50-74 years with a positive result from an FIT (> 15 mu g hemoglobin/g feces) and subsequent colonoscopy (reference standard) were included. Those who used regular aspirin, warfarin, or direct-acting oral anticoagulants (DOACs) were defined as users. Non-users were matched according to age, sex, screening center, and screening round. The primary outcomes were the positive predictive value (PPV) for CRC and advanced adenoma. RESULTS: Among 4908 eligible participants, 1008 used aspirin, 147 used warfarin, 212 used DOACs, and 3541 were non-users. CRCs were found in 234 individuals and advanced adenomas in 1305 individuals. The PPV for CRC was 3.8% for aspirin users vs 6.4% for matched non-users (P = .006), The PPV for advanced adenoma in aspirin users was 27.2% vs 32.6% for matched non-users (P = .011). For DOAC, the PPV for CRC was 0.9% in users vs 6.8% in matched non-users (P = .001). The PPV for advanced adenoma in DOAC users was 20.5% vs 32.4% in matched nonusers (P = .002). There was no significant difference in PPV for CRC or advanced adenoma in warfarin users compared to nonusers. CONCLUSIONS: In a large screening cohort in Norway, regular use of aspirin and particularly DOACs, were associated with lower PPV of FIT for detection of CRCs and advanced adenomas.