Outcome of colorectal cancer screening by digital rectal examination in asymptomatic average-risk individuals

Background: In clinical practice, asymptomatic individuals with a positive fecal occult blood test (FOBT) obtained by digital rectal examination (ORE) are often referred for a colonoscopic evaluation. Although widely practiced, this screening method has been discouraged because it is thought to increase the false positive rate of FOBT. Our purpose was to compare the predictive value of a positive FOBT obtained by ORE with that obtained from spontaneously passed stools (SPS). Methods: Asymptomatic average-risk patients over the age of 50 years with a positive FOBT obtained by DRE or SPS who were referred for colonoscopy from 1/92 to 1/97 were identified. FOBT was performed using Hemoccult test kits without rehydration. Patient charts, endoscopy records, and pathology reports were reviewed. The cost of endoscopy was estimated by adding the physician fee under Medicaid reimbursement, the facility fee, and the pathology fee. Results: 672 consecutive patients (371M; 301F) were evaluated by colonoscopy. DRE (N=282) SPS (N=390) Mean age, years 63.2 (50-91) 62.3 (50-88) PPV for neoplasms 44.3% 44.9% False positive FOBT 55.7% 55.1% Neoplastic lesions 125 (44.3%) 175 (44.9%) All adenomatous polyps 111 (39.4%) 151 (38.7%) Adenoma ≥ 1 cm 29 (10.3%) 47 (12.1%) Adenocarcinoma 33 (11.7%) 44 (11.3%) Nonneoplastic lesions 86 (30.5%) 125 (32.1%) Normal colonoscopy 107 (37.9%) 142 (36.4%) Cost per neoplasm $2.007.67 $1,964.80 Cost per adenoma ≥ 1 cm $8,653.74 $7,315.74 Cost per adenocarcinoma $7,604.80 $7,814.54 Conclusions: The predictive value of a positive FOBT performed on stool obtained by DRE is no different from that obtained by SPS in asymptomatic average-risk individuals. Furthermore, FOBT of stool obtained by DRE does not increase the rate of false positive tests or the cost per cancer detected by colonoscopy. In this patient population, all individuals with a positive FOBT obtained by either DRE or SPS should be evaluated by full colonoscopy.