Probing the Occult: Testing for Blood in the Stools
- Denis M. McCarthy
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In this issue, Sawhney et al.  draw attention to the reduced positive predictive value (PPV) of fecal occult blood testing (FOBT) for advanced colonic neoplasia, associated with patient use of aspirin, NSAIDs, warfarin, or clopidogrel compared to controls. The control group is already compromised by the fact that 48% of them apparently used some non-prescription NSAIDs (see discussion). Thus, the rate in true controls not using NSAIDs is probably higher, making the likely reductions in PPVs even greater than those reported. The FOBT used was Hemoccult II (Beckman Coulter Incorporated, Fullerton, CA) without re-hydration, but the findings appear likely to apply to the same or greater degree to hydrated specimens or to other more sensitive guaiac-based tests (g-FOBTs), e.g., Hemoccult SENSA. The effect of clopidogrel on PPV is particularly striking.
If, as the authors claim, FOBT remains in wide use in screening for colorectal cancer (CRC), these findings are very important, and imply ...
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- Probing the Occult: Testing for Blood in the Stools
Digestive Diseases and Sciences
Volume 55, Issue 6 , pp 1503-1505
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- Denis M. McCarthy (1) (2)
- Author Affiliations
- 1. Raymond G. Murphy VA Medical Center–111F, 1501 San Pedro Blvd. SE, Albuquerque, NM, 87108, USA
- 2. Division of Gastroenterology & Hepatology, University of New Mexico School of Medicine, Albuquerque, NM, USA