Fecal occult blood testing - as its name implies - can provide clues as to subtle blood loss in the, anywhere from the to the. Positive tests ("positive stool") warrant further investigation for or a (such as or ).
In the event of a positive faecal occult blood test, the next step in the workup is a form of visualization of the gastrointestinal tract by one of several means:
An examination of the rectum and lower colon with a lighted instrument to look for abnormalities, such as polyps.
A more thorough examination of the rectum and entire colon.
Annual testing of a population may reduce the mortality associated with colon cancer by a third, depending on the incidence of gastrointestinal cancer in that population. It is not always cost effective to a large population.
If colon cancer is suspected in an individual (such as in someone with an unexplained ) faecal occult blood tests are typically not warranted. If a doctor suspects colon cancer, more rigorous investigation is necessary, whether or not the test is positive.