An assessment of an immunochemical test for human haemoglobin in the detection of colonic polyps

It is now widely accepted that malignant tumours of the colon and rectum almost invariably arise from pre-existing adenomatous polyps. If such polyps could be detected and removed colonoscopically before they become malignant, theoretically the incidence of invasive colorectal cancer could be dramatically reduced. The purpose of this study was to determine whether an immunochemical test for faecal occult blood would identify patients with benign colonic polyps. The faecal samples from 121 patients scheduled to undergo colonoscopy were tested by our immunochemical method and the Hemoccult II test. There were nine patients who had malignant colorectal tumours. These were excluded from this study. Twenty-nine were found to have colonic polyps. Fifteen of these had one or more faecal samples which were positive by the immunochemical test. In contrast, there was only one patient who had a positive Hemoccult II test. Fourteen of the remaining 83 patients had positive immunochemical tests. The findings on colonoscopy provided satisfactory explanations in all these cases. Polyps of all sizes and histological type were associated with positive immunochemical tests. It is concluded that the immunochemical test has sufficiently high sensitivity for colonic polyps to make feasible the screening of patients at high risk of developing colonic cancer.