New screening method for occult gastrointestinal bleeding: immunologic and guaiac slide tests

A valid mass screening method for occult, bleeding gastrointestinal pathology including colorectal cancer should be monospecific for human hemoglobin, sensitive for approximately 3 mg of human blood per 1 g of stool, capable of differentiating upper and lower gastrointestinal bleeding, cost effective, uncomplicated, and acceptable to patients. Hemoccult II, a guaiac peroxidase detection test, is nonspecific for human blood and cannot differentiate between upper and lower gastrointestinal bleeding. A radial immunodiffusion slide test for detecting human hemoglobin was compared with a guaiac test over a four-year period in 211 patients. in gastrointestinal problems diagnosed by endoscopy, roentgenographic rays, and other procedures, the Hemoccult II was positive in 9 of 41 cases of upper gastrointestinal tract origin (21 percent detection rate), whereas the radial immunodiffusion method, expected to be negative as a result of action of gastrointestinal proteases, was positive in only 3 and negative in 38 of the 41 samples (92 percent accuracy). The two tests were equally effective in detecting lower gastrointestinal bleeding (14 of 37 samples, 37 percent accuracy). The findings of this study indicate that the immunologic test may remedy the deficiencies of the guaiac test. The concomitant use of the immunologic and appropriately sensitive guaiac test appears to fulfill screening test requisites.