Do aspirin and nonsteroidal anti-inflammatory drugs cause false-positive fecal occult blood test results? A prospective study in a cohort of veterans.

PURPOSE To determine whether use of regular aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) is a risk factor for a false-positive fecal occult blood test result. METHODS Consecutive patients referred for colonoscopy for a positive fecal occult blood test result at a Veterans Affairs hospital were eligible. Patients with hematochezia, peptic ulcer disease, or unevaluated dyspepsia requiring antacids, or who used warfarin, were excluded. Regular aspirin and NSAID use was defined as at least one daily dose for at least 3 days per week. Colonoscopic findings unlikely to explain a positive test result alone were defined a priori as diverticulosis, hemorrhoids, or polyps <1.0 cm with no villous histology. Findings likely to explain a positive test result included cancer and advanced polyps. RESULTS The sample comprised 193 veterans with a mean (+/- SD) age of 66 +/- 10 years; 98% were male and 86% were white. No colonoscopic findings explained the positive fecal occult blood test result in 153 patients (79%). One hundred and thirty-five patients (70%) were regular aspirin or NSAID users, of whom 21% (n = 29) had findings to explain the positive test results, compared with 19% (11/58) of nonusers (P = 0.7). There was no relation between aspirin dose and colonoscopic findings unlikely to explain a positive test result. Multivariate analysis found no association between regular aspirin or NSAID use and a false-positive test result (odds ratio = 0.85; 95% confidence interval: 0.39 to 1.84). CONCLUSION Aspirin and NSAID use were not risk factors for a false-positive fecal occult blood test result in this study.