Results of fecal immunochemical tests for colorectal cancer screening not affected by NSAIDs, aspirin, or anticoagulants

Reference

Nieuwenburg SA, Vuik FE, Kruip MJ, Kuipers EJ, Spaander MC. Effect of anticoagulants and NSAIDs on accuracy of faecal immunochemical tests (FITs) in colorectal cancer screening: a systematic review and meta-analysis. Gut 2019;68(5):866-872

Synopsis

Prevous research has shown that approximately 6.2% of screening FIT results are positive, with a positive predictive value (PPV) of 35% to 55%. These authors wondered whether the use of something that can make you bleed would reduce the PPV by making benign lesions more likely to bleed (leading to more false-positive results), or whether it would increase the PPV by making precancerous and malignant lesions more likely to bleed? They did a careful search of the literature and identified 8 studies with 2022 patients that compared the accuracy of the FIT in a screening population of patients taking an oral anticoagulant or an NSAID with those not taking either drug. Of the 8 studies, all but one were done in Europe (the eighth was in Hong Kong), most used a FIT cutoff of 15 to 20 mcg Hb/g. Six studies included aspirin users, 4 included oral anticoagulant users, and 1 included NSAID users (3 of the studies included more than one medication). The authors found no consistent effect on PPV among users and nonusers of oral anticoagulants and NSAIDs, and in general the differences were small. For example, the pooled PPV for advanced neoplasia was 38.2% in aspirin/NSAID users and 39.4% in nonusers. The PPVs for colorectal cancer in oral anticoagulant users and nonusers were 5.7% and 6.2%, respectively. And the PPVs for advanced neoplasia in oral anticoagulant users and nonusers were 37.6% and 40.3%, respectively.