a test to check for blood in the stool. a brush is used to collect water drops from around the surface of a stool while it is still in the toilet bowl. the samples are then sent to a laboratory, where they are checked for a human blood protein. blood in the stool may be a sign of colorectal cancer. also called immunoassay fecal occult blood test, immunochemical fecal occult blood test, and immunologic fecal occult blood test.