Anticoagulant or aspirin treatment does not affect the positive predictive value of an immunological fecal occult blood test in patients undergoing colorectal cancer screening

Abstract

The immunochemical fecal occult blood test (i-FOBT) is widely used as a recommended screening strategy for colorectal cancer (CRC). A growing number of patients potentially targeted by CRC screening programs are on oral anticoagulant or chronic low-dose aspirin therapy, mainly for primary or secondary cardiovascular prophylaxis. This study aims at evaluating whether the use of these medications may impact on the diagnostic performances of i-FOBT for CRC screening. All i-FOBT-positive patients on anticoagulant or chronic low-dose aspirin therapy recorded in a regional mass screening program database were enrolled as cases. Control groups were derived from the same database and included drug-naive i-FOBT-positive patients, matched in a ratio of 1 : 2 for age (± 3 years of age), sex, date of colonoscopy, and practice site. Information about the use of medications was collected by cross-checking patients' interview before colonoscopy and data recorded in the provincial electronic registry of medical prescriptions. The positive predictive value of i-FOBT for significant neoplasia (high-risk adenoma and CRC) was calculated in the case and control groups. In a 2-year study period, 2376 patients were recorded in the regional database. Of these patients, 53 (2%) were on anticoagulation (control group of 106 patients) and 172 (6.6%) were on chronic low-dose aspirin treatment (control group of 344 patients). Significant neoplasia was detected in 15 (28.3%) patients on anticoagulants and in 37 (34.9%) corresponding controls (P=0.45). Significant neoplasia was detected in 50 (29.1%) patients on chronic low-dose aspirin and in 107 (31.1%) corresponding controls (P=0.64). The positive predictive value of i-FOBT for significant neoplasia is not affected by ongoing anticoagulant or chronic low-dose aspirin therapy. This finding suggests that there is no need to interrupt these treatments before i-FOBT for CRC screening.