Faecal occult blood is a term for blood present in the faeces that is not visibly apparent. In medicine, a faecal occult blood test is a check for hidden (occult) blood in the stool (feces). Conventional faecal occult blood tests look for heme. Newer, modern tests look for globin.

Uses

Fecal occult blood testing - as its name implies - can provide clues as to subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon. Positive tests ("positive
stool") warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer).

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:

1. Sigmoidoscopy, an examination of the rectum and lower colon with a lighted instrument to look for abnormalities, such as polyps.
2. Colonoscopy, a more thorough examination of the rectum and entire colon.
3. virtual colonoscopy
4. Endoscopy
5. Double contrast barium enema: a series of x-rays of the colon and rectum.

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 screen a large population.

If colon cancer is suspected in an individual (such as in someone with an unexplained anaemia) 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.

Methodology