Occult Blood Test

Cancer is the third leading cause of mortality and morbidity in the Philippines. The leading cancer types are lung, breast, cervix, liver, colon, and rectum. The Philippine Cancer Control Program that was launched in 1988 utilizes primary, secondary and tertiary prevention. Among the primary preventive measures are cancer education and early detection of cancer. One simple laboratory method that can detect, in particular, colon and rectum cancer, is fecal occult blood test (FOBT).

What is FOBT?

Fecal occult blood test is a laboratory test used to check stool samples for hidden (occult) blood. Occult blood or hidden blood in the stools is passed in such small amounts that are not visible through the naked eye and may only be detected through the chemicals used in FOBT.

What does fecal occult blood indicate?

Occult blood in the stool indicates colon cancer or polyps in the rectum or colon. A Polyp in the colon and rectum can be a precursor to cancer. Fecal occult blood indicates the presence of bleeding. It does not indicate the source of bleeding. Thus, a positive result in FOBT would give an indication or signal for further examination to determine the source of bleeding.

Other conditions wherein FOBT may be indicated?

Aside from colon and rectal cancer, your doctor might request for FOBT if you have unexplained anemia. FOBT can determine whether the cause of anemia is due to bleeding in the digestive tract, as an example, in a case of bleeding ulcer.

Is the test always accurate?

No. The test may give false-negative result when it shows a negative result in the presence of cancer or polyps that don't bleed. It could yield a false-positive result if the test shows a positive result and you have no cancer. The positive result might have come from other conditions, like hemorrhoid, stomach ulcer, or even blood swallowed from some conditions like dental and gum problems and nose bleeding. Various foods, dietary supplements and medications can also affect the results of fecal occult blood test.

Can fecal occult blood test detect all types of colon and rectal cancers?

No. There are some colon and rectal cancers that can be detected by colonoscopy and may not be detected by fecal occult blood test.

How often does one have FOBT?

If you're age 50 and older and you are at average risk of colon cancer, your doctor may request for FOBT every year to screen for colon cancer. In addition, your doctor might need to request other screening test to examine the colon and rectum directly.