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Does warfarin therapy affect the yield of fecal occult blood tests (FOBTs) for colorectal cancer screening? In theory, warfarin could either facilitate detection of true positives (by preferentially inducing bleeding from colorectal neoplastic lesions) or lead to false positives (by preferentially inducing bleeding from other gastrointestinal sources).
In this study, 10,266 patients at 68 U.S. sites underwent colonoscopy to evaluate positive FOBTs; 4% of patients were using warfarin when their FOBTs were performed. The prevalence of a large polyp (≥10 mm) or suspected cancer that was visualized by colonoscopy was significantly higher in the warfarin group than in the no-warfarin group (16% vs. 11%). However, after adjustment for age, sex, an…