Background: Testing stool for occult blood at the time of digital rectal examination (DRE) has been discouraged because it is thought to increase the number of false-positive test results.
Objective: To compare the diagnostic yield of colonoscopy and the cost per cancer detected in asymptomatic patients with a positive fecal occult blood test result obtained by DRE with that obtained from spontaneously passed stool (SPS) samples.
Methods: We reviewed the medical records of consecutive asymptomatic patients at average risk for colorectal cancer who were referred for colonoscopy to evaluate a positive fecal occult blood test result obtained by DRE (n = 282) or SPS samples (n = 390). The cost of colonoscopy was estimated by adding the physician fee under Medicaid reimbursement, the facility fee for endoscopy, and the pathology fee for the biopsy specimens.
Results: During the 5-year study period, 672 patients were evaluated and a colonic source of occult bleeding was identified in 145 patients (21.6%). The predictive value of a positive fecal occult blood test result (22.0% vs 21.3%, P = .85) and the cost per cancer detected ($7604.80 vs $7814.54) were no different in the DRE and SPS groups, with carcinomas being detected in 11.7% and 11.3% of patients, respectively.
Conclusions: Testing stool for occult blood at the time of DRE does not increase the number of false-positive test results or the cost per cancer detected in asymptomatic patients at average risk for colorectal cancer. In this patient population, all individuals should be evaluated by full colonoscopy regardless of the method of stool collection.