183 HOME FECAL OCCULT BLOOD TESTING LACKS SPECIFICITY FOR ADENOMATOUS POLYPS IN AVERAGE-RISK VETERANS BEING SCREENED FOR COLORECTAL NEOPLASIA

ObjectiveColorectal cancer (CRC) screening using home fecal occult blood testing (FOBT) is being used in many VA hospitals as a screening tool since it has been shown to reduce mortality in average-risk individuals. It is not clear, however, whether a positive test result truly selects for patients with premalignant lesions or simply targets them for further examination that ultimately identifies randomly present lesions. Our hypothesis is that FOBT in asymptomatic VA patients does not selectively identify individuals with premalignant adenomas.MethodsWe retrospectively reviewed the Clinical Outcomes Research Initiative (CORI) endoscopic database at the Memphis VAMC for patients who had undergone colonoscopy between 1999 and 2005 for a "positive home FOBT. " Patients with anemia, prior history of colon polyps or CRC, family history of colon polyps or CRC, or any symptoms that would have prompted colonoscopy, including abdominal pain, weight loss, change in bowel habits, loss of appetite, and rectal bleeding, were excluded after careful review of their medical record in the VA Computerized Patient Record System (CPRS). Prevalence of adenomatous polyps and CRC in the FOBT+ group was calculated and compared to a cohort of asymptomatic patients who underwent screening colonoscopy with the same exclusion criteria.ResultsFrom the CORI endoscopic database, 663 and 301 patients were identified as having undergone colonoscopy for positive FOBT and screening, respectively. CPRS narrowed the FOBT cohort to 147 (45 were black and 102 were white) and the screening colonoscopy cohort to 138 (36 were black and 102 were white). All veterans were male. The findings are summarized in tabular form. Of the FOBT(+) patients with advanced lesions, 41.6% were on antiplatelet agents at the time of FOBT.ConclusionThe prevalence of adenomatous polyps in individuals screened by FOBT does not differ from the prevalence in a comparable screening colonoscopy control group. However, individuals screened by FOBT tended to have more advanced neoplasms as defined by polyps size >/= 10 mm and/or colon cancer compared to screening colonoscopy. Antiplatelet agents usage may contribute to the increased FOBT positivity in those with advanced lesions.