The value of a positive fecal occult blood test (FOBT) found at the time of digital rectal examination is disputed. To determine the significance of a positive FOBT obtained in this manner, the records of 270 patients who underwent colonoscopy for any positive FOBT were retrospectively reviewed. Occult blood was found in 144 patients at the time of digital rectal examination and in 126 individuals after they submitted three spontaneously passed stool specimens. Of the patients with a positive FOBT on rectal examination, 77% were hospitalized at the time compared with only 17% of those with positive FOBTs from spontaneously passed stools. The frequency of colonic abnormalities was similar with both stool collection methods in inpatients and outpatients. No statistically significant differences in neoplastic polyp or colon cancer detection rates, nor in the finding of hemorrhoids or other anorectal abnormalities, were apparent. Therefore, the belief that a positive FOBT found at the time of digital examination can or should be discounted as a false positive (because of the presence of hemorrhoids or other lesions prone to trauma at the time of digital examination) was not substantiated by this study.
(Arch Intern Med. 1991;151:2180-2184)