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Don’t Blame Warfarin for Occult Fecal Blood

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Patients on warfarin need not discontinue treatment when they have a fecal occult blood test (FOBT), as it does not affect the predictive accuracy of the test for identifying colorectal neoplasms, according to findings reported in an August 3rd online publication of the American Journal of Gastroenterology.

Dr. Judy F. Collins and colleagues at Oregon Health and Science University and the Portland VA Medical Center point out that warfarin increases the risk of overt GI bleeding, but little is known about occult bleeds. While many physicians discontinue warfarin before FOBT on the assumption that it would increase the false-positive rate, current guidelines do not address the issue.

The researchers therefore looked at findings in 10,266 patients undergoing colonoscopy solely on the basis of a positive FOBT; 372 of the subjects were on warfarin and 629 were excluded because their warfarin status was not documented.

Colonoscopy found a polyp > 9 mm or a suspected malignant tumor in 16.1% of the warfarin group and 11.4% of the non-warfarin group. However, after adjustment for age and sex, the likelihood of significant findings was no different in the two groups (odds ratio 1.1).

“On the basis of our retrospective study, the positive predictive value of the guaiac FOBT for significant colon pathology is not affected by the use of warfarin at the time of FOBT,” the investigators conclude. “These data support the practice of continuing warfarin before and during FOBT and avoiding any potential risk associated with the discontinuation of warfarin.”

Am J Gastroenterol 2010.