Contributed by – Healthians Team
What is the fecal occult blood test?
A fecal occult blood test is used to check the stool samples for hidden blood in it. Hidden blood is the blood that cannot be seen with naked eyes. Now, there can be many reasons behind the presence of blood in the stool. But, out of all those causes, the important one is the presence of polyps or colon cancer in the digestive tract.
Polyps are finger-like growths that protrude into the cavity of the colon or the rectum. Although these growths are common in people as they age, polyps can become cancerous and even spread to other parts of the body. The good thing about colon cancer is the fact that it is treatable, provided it is detected on time. Here, the fecal occult blood test can be used as a colon cancer screening tool.
Who should get a fecal occult blood test?
A fecal occult blood test is one way of screening people for colon cancer. Those who are at average risk of colon cancer and have no symptoms should get a fecal occult blood test done regularly. People without any family history of colon cancer and those without certain genetic diseases are considered to be at average risk.
Why is the fecal occult blood test needed?
Blood in the stool may be the first or sometimes the only sign of polyps or colon cancer. This is why this test is a valuable screening tool. If detected on time, the treatment can begin quickly which increases the chance of cure.
The test may also be used to diagnose other conditions that cause bleeding in the digestive tract. Some such conditions are –
- Hemorrhoids
- Anal fissures
- Intestinal infections
- Ulcers
- Ulcerative colitis
- Crohn’s disease
- Diverticular disease
- Abnormalities of the blood vessels in the large intestine
Besides, the doctor may order this test in case of unexplained anemia that might be caused by bleeding in the digestive tract.
What does fecal occult blood test results mean?
A negative fecal blood test result means that no blood was detected in the stool sample at the time of the test. While a positive result means that the stool sample had blood in it.
In case of a positive result, follow up tests will be needed to find the exact cause of bleeding.
Note, that there are high chances of getting a false-negative because polyps bleed intermittently. If the sample collection is done on the day when they were not bleeding, the result will come out negative even when a condition exists.
Getting a false-positive result is also possible because blood from nose bleeds, gum bleeds or that in food such as meat may also get detected in the test. However, it can be avoided by going for a different type of fecal occult blood test.
How is the fecal occult blood test done?
For a fecal occult blood test, your healthcare provider will give you a kit which will include instructions that you’ll have to follow to collect the sample. The kit will then be sent to a lab for testing.
Usually, there are two main fecal occult blood test methods. Both of them are designed to detect hemoglobin – a molecule present in red blood cells. Now, hemoglobin has two parts – heme and globin. Each test detects a different part of the molecule.
- Immunochemical fecal occult blood test (iFOBT or FIT) – It checks for the globin part of the hemoglobin. This test has been specifically designed to detect human globin. This means that globin from non-human blood such as meat will not be detected and the results are almost always accurate.
- Guaiac fecal occult blood test (gFOBT or FOBT) – It checks for the heme part of hemoglobin from blood in the stool. The limitation of this test is that it can detect blood from any source, thereby causing false-positive test results. Some foods and medications can also interfere with this test.
If you are going for FIT, then there are no particular restrictions before the test. However, in the case of FOBT, take care of the following –
- Avoid introducing blood from any other source to your digestive tract for a few days before the test. This includes avoiding various meats.
- Avoid having dental procedures a few days before the test.
- Any stomach bleeds such as ulcers should be controlled.
- Avoid non-steroidal anti-inflammatory drugs because they may trigger stomach bleeds.
- Avoid foods such as broccoli, turnips, cauliflower, and apples.
- Fruit juices and vitamin C supplements should be avoided.
Furthermore, remember to inform your doctor about any prior medical condition or about the medications you are taking because they can influence your test results.
