Mass screening for colorectal cancer by testing for occult blood under restricted diet and a questionnaire in Osaka.

: Because of the recent increase in the incidence of colorectal cancer in Japan, attempts were made to find an effective method for screening asymptomatic patients with this cancer. A total of 12,520 participants in Osaka were screened in a 2-year program from April 1982 by a test of fecal occult blood under a restricted diet, and a medical questionnaire. Occult blood in feces was examined for 3 consecutive days using one guaiac-impregnated slide (Shionogi B) each day. This slide was about twice as sensitive as the Hemoccult slide. Further diagnostic workups were required in 3,452 individuals, of which 2,602 (75.7%) were due to positive occult blood. Proctosigmoidoscopy was performed in 2,214 (64.4%) of these persons, barium enema in 1,397 persons, and flexible colonoscopy in 187 persons. Colorectal cancers were detected in 18 patients (0.14% of the total screened); ten of these cancers were in an early stage. Thus this screening method is reliable for detecting asymptomatic cancer of the colon and rectum.