A test that checks for occult (hidden) blood in the stool. Small samples of stool are placed on special cards and sent to a doctor or laboratory for testing. An antibody that binds to a blood protein called hemoglobin is used to detect any blood. Blood in the stool may be a sign of colorectal cancer or other problems, such as polyps, ulcers, or hemorrhoids. Also called fecal immunochemical test, FIT, immunoassay fecal occult blood test, immunochemical fecal occult blood test, and immunologic fecal occult blood test.