Objective Although home-based fecal occult blood testing (FOBT) is widely used to screen for colorectal cancer and adenomatous polyps and has been shown to reduce mortality from colorectal cancer (CRC), it is not clear whether a positive test result is truly selecting for patients with these conditions or is simply targeting patients for further examination that ultimately identifies randomly present lesions. Our hypothesis is that FOBT in asymptomatic VA patients does not selectively identify individuals with colorectal neoplasia.
Methods We retrospectively reviewed the Clinical Outcomes Research Initiative (CORI) endoscopic database at the Memphis VAMC for patients who underwent colonoscopy between 1999-2004 for “positive 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). Patients with occult positive stool following digital rectal examination were also excluded. Age-based prevalence rates for adenomatous polyps and CRC were calculated and compared to historical controls from autopsy studies. The effect of race and NSAID usage on results was also examined.
Results From the CORI endoscopic database, 663 patients were identified as having undergone colonoscopy for positive FOBT. CPRS chart review narrowed the analysis group to 151 asymptomatic individuals at average risk for CRC. Of these 151 patients, 50 were black and 101 were white. Almost all were male. The findings are: (table)
Race and NSAID use did not alter the distributions above. Historical prevalence rates from autopsy studies for adenomatous polyps in males > 50 YOA are 40-50% and for CRC is 3-4%.
Conclusion The prevalence of adenomatous polyps and CRC in asymptomatic, average-risk VA patients with positive home FOBT does not appreciably differ from prevalence rates reported in autopsy studies.