[Screening for colorectal tumors using fecal occult blood studies]

Guaiac tests such as Hemoccult are widely used but are affected by several factors. Occult blood testing does uncover subclinical colorectal cancer often at early stage, but a favorable effect on survival remains to be proven. The sensitivity for the detection of malignancies is from moderate to good, but it is poor for benign polyps. Predictive value of a positive test for cancer ist about 8-12%. Thus, most of the individuals with a positive test would not need colonic investigations. Recommendations relating to the testing for of occult blood could change rapidly with the new immunologic techniques or with new data on mortality coming from controlled clinical trial now being conducted.