A case control study to evaluate the occult blood screening for colorectal cancer was conducted in a town where colorectal cancer screening had been performed by Hemoccult test during the early years and subsequently by an immunochemical hemagglutination test. All residents aged >/=40 years had been offered the annual screening. Case series consisted of 51 subjects with fatal colorectal cancer. Three controls per case were selected from the list of residents who were alive at the time of diagnosis of the corresponding case and had been living in the town, matched by gender and by age. The odds ratio (OR) of dying of colorectal cancer for those having their most recent screening histories with Hemoccult test or the immunochemical test during the preceding 1 year and 1-2 year segment before case diagnosis were 0.20 [95% confidence interval (CI): 0.08-0.49] and 0. 17 (95% CI: 0.04-0.75), respectively. The OR increased towards 1.0 as the number of years since the most recent screening increased. The OR of dying of colorectal cancer was calculated to be 0.19 (95% CI: 0.05-0.70) for those screened with the immunochemical test alone during the preceding 1 year after adjustment for previous screening histories with the Hemoccult test. Corresponding OR was 0.36 (95% CI: 0.11-1.17) for those screened with Hemoccult test during the preceding 1 year. These results suggest that screening for colorectal cancer by fecal occult blood testings or immunochemical test alone would reduce mortality and that efficacy of the screening would be higher for the immunochemical test than for Hemoccult test.

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