[Evaluation of an immunological test for detecting occult fecal blood for case-finding in colorectal tumors].

Screening for colorectal tumours (cancers and polyps) by searching for blood in stools using the gaiac test is a well-known method. We evaluated a new gaiac test, the originality of which from its coupling with an enzyme immuno-assay specifically measuring human hemoglobin (Fecatest). The objectives of this new test were to decrease false positives and thus to improve the positive predictive value of screening. Subjects over 45 years of age attending health examinations at a Center of Preventive Medicine were studied. Of the 5,185 subjects who received the test, 4,376 (84 p. 100) performed it correctly, demonstrating good compliance in this population. For 664 (15 p. 100), the results of the gaiac test were positive. This positivity rate was higher for men than for women (20 p. 100 vs. 10 p. 100) but was not influenced by age. After positive results, 471 (70 p. 100) patients completed investigations decreasing the overall compliance to 80 p. 100. Fifteen cases of cancer and 78 cases of adenomas were found. The positive predictive value of the test was 20 p. 100 for tumours. A benign cause was found in 44 p. 100 of 471 patients, and investigations were negative in 36 p. 100. When the gaiac test was positive, the immunoenzymatic method significantly improved the positive predictive value for cancer (6 p. 100 vs. 3 p. 100) but not for polyps (20 p. 100 vs. 17 p. 100). Three of the 15 cancers and half of the 78 adenomas would not have been discovered with the immunoenzymatic method.(ABSTRACT TRUNCATED AT 250 WORDS)