Immunochemical versus guaiac occult blood stool tests: results of a community-based screening program

This study was designed to investigate two guaiac-based and one immunochemical faecal occult blood test in a community screening program. A total of 39,000 test kits consisting of Hemoccult II^®, Hemoccult Sensa^® and HemeSelect^® were distributed and of these 8933 (23%) were returned for testing. Follow-up contact with 1165 individuals who tested positive on at least one of the nine test slides was successful in 1076 cases (92.4%). Physician verification in 631 individuals revealed 25 patients (4%) diagnosed with colorectal cancer and 145 (23%) with polyps, of which 120 (82.7%) were adenomatous. The percentage of smaller adenomatous polyps detected relative to the percentage of large polyps (>1 cm) was: Hemoccult II^® 31% versus 60%, Hemoccult Sensa^® 73% versus 80% and HemeSelect^® 34% versus 57%, respectively. The proportion of adenomatous polyps greater than 2 cm detected by individual tests was even more striking with Hemoccult II^® positive for 83%, Hemoccult Sensa^® for 100% and HemeSelect^® for 75%. Of the 25 patients diagnosed with cancer, 17 (68%) were diagnosed with early-stage disease. A statistically signficant trend (P < 0.001) was observed with positive predictive values ranging from 3.3% for individuals with only one positive test to one approaching 40% for individuals with 7 or more positive tests. In this study, the most sensitive predictor of colorectal cancer was found to be the combination of Hemoccult II^®/HemeSelect^®. While there was no increase in the positive predicted value for adenomatous polyps <-1 cm, there was a direct linear increase for adenomatous polyps >1 cm.