Definition of Fecal occult blood test (FOBT):

A fecal occult blood test (FOBT) is a noninvasive test (nothing enters the body). This test detects hidden (occult) blood in the stool. Such blood may come from anywhere along the digestive tract. Hidden blood in stool is often the first, and in many cases the only, warning sign that a person has colorectal disease, including colon cancer.

How the test is performed:

There are two types of FOBTs: 1) the traditional guaiac smear test (Hemoccult, Seracult, Coloscreen), and 2) the newer, flushable reagent pads (EZ DetectT, ColoCARE). They are both useful in detecting hidden blood in the stool, and are mainly used for colorectal cancer screening.

The tests differ in the way they are performed. The flushable reagent pads are available without a prescription at many drugstores. In contrast, the traditional guaiac smear test is completed and interpreted by a medical professional, and these tests are usually available from a laboratory or a doctor's office.

Many consumers prefer the flushable reagent pads because there is no stool handling and no laboratory processing. However, health care providers usually favor the guaiac tests because the large studies that have shown the benefits of colon cancer screening were done with guaiac tests.

See description under specific type of FOBT for how these tests are performed.

How to prepare for the test:

See description under specific type of FOBT.

How the test will feel:

See description under specific type of FOBT.

Why the test is performed:

This test is mainly performed yearly for colorectal cancer screening. It may also be performed in the evaluation of anemia.

Advantages:

• Noninvasive
• Low cost

Disadvantages:

• Detects blood in stool, but not its cause.
• False-positive results are common with some testing methods. This may cause unneeded anxiety about cancer and lead to unnecessary further tests.
• False-negative results are also common and may miss disease in its early stages.