Faecal Occult Blood Test: What to Expect

What is a faecal occult blood test?

A faecal occult blood test (FOBT) is a laboratory test used to detect the presence of blood in your stool sample. The term "occult" refers to blood that is not visible to the naked eye or blood that is 'hidden'. There are two main types of FOBT: the guaiac-based test (gFOBT) and the immunochemical test (iFOBT or FIT).

What is it used for?

People commonly use this test as a screening tool to identify small amounts of blood that could potentially indicate a digestive tract problem such as colorectal cancer or colon cancer.  A faecal occult blood test is one option for colon cancer screening in people who don't showcase any symptoms. Occult blood in the stool may be a sign of cancer or precancerous polyps in the colon or rectum. However, it is important to note that not all cancers or polyps bleed.

Occasionally, it is used to investigate the cause of unexplained anaemia or to help distinguish between different types of bowel disorders. If a faecal occult blood test detects blood, additional tests are needed to find the source of the bleeding. A faecal occult blood test can only detect if blood is present or not. It cannot locate the source of the bleeding.

A faecal occult blood test should also not be used if you have colon cancer symptoms. These symptoms may include blood in your stool or in the toilet, pain in your abdomen, and a change in bowel habits. People with a high risk of colon cancer, including those who have a history of colon polyps and those with a close family member who has had colon cancer, are also not eligible for this test.

Please speak with your healthcare provider about any symptoms you are experiencing and if you are considering taking an FOBT test. Request an appointment with Thomson Medical today.

Why do I need a faecal occult blood test?

If you are over 50 years old, have a family history of colorectal cancer, or are experiencing unexplained anaemia, your doctor may recommend an FOBT. The test is also used as a routine screening measure to detect bowel cancer early, when treatment is most effective. However, if you already have symptoms such as visible blood in your stool or significant changes in bowel habits, your doctor may suggest more direct investigations, such as a colonoscopy, instead of an FOBT.

How do I prepare for the test?

Preparation depends on the type of FOBT being used:

• Immunochemical FOBT (iFOBT or FIT):

  • Usually, no special dietary or medication restrictions are required.

• Guaiac FOBT (gFOBT):

  • You may be asked to avoid certain foods and medications for a few days before the test, as they can affect the results. These include red meat, certain raw fruits and vegetables, vitamin C supplements, iron supplements, and non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen. Ingesting these before the test may cause either a false positive or a false negative test.

Always follow the specific instructions provided by your healthcare professional or the test kit.

What happens during a faecal occult blood test?

Your healthcare provider typically provides a kit for you to use at home during the test. The process usually involves:

• The process involves collecting small samples of stool from different bowel movements, often over three separate days.

• Transfer a small amount of stool onto a test card or into a collection tube using a spatula, stick, or applicator.

• You should seal the samples and send them back to your healthcare provider or laboratory for analysis.

• The laboratory will then test the samples for the presence of hidden blood.

The kit typically includes everything you need to complete the test and instructions to explain the process. For best results, follow the instructions that come with your test kit.

What do the results mean?

• Negative result:

  • No blood was detected in your stool. This is considered normal, but regular screening may still be recommended if you are at average risk for bowel cancer.

• Positive result:

  • Your stool contained blood. This does not necessarily mean you have cancer. Other causes include polyps, haemorrhoids, ulcers, diverticular disease, and inflammatory bowel disease. Further tests, such as a colonoscopy, will be needed to determine the source of the bleeding.

False positives and false negatives can occur, especially if the preparation instructions are not followed properly.

Are there any risks to the test?

There are no physical risks associated with collecting stool samples for a faecal occult blood test. However, the test is not perfect and may not detect all cases of bowel cancer or other conditions. It can also produce false-positive or false-negative results, leading to unnecessary further testing or missed diagnoses.

Your doctor can help you understand the benefits and risks of an FOBT screening and determine whether it is appropriate for you based on your individual risk factors and preferences.

FAQ

What does a faecal occult blood test look for?

A faecal occult blood test looks for hidden blood in the stool, which may be a sign of bleeding in the digestive tract due to conditions such as polyps, cancer, ulcers, or inflammatory bowel disease.

What happens if the faecal occult blood test result is positive?

If the test is positive, your healthcare provider will usually recommend further investigations, most commonly a colonoscopy, to identify the source of the bleeding and determine if it is due to a serious condition such as cancer or a more benign cause like haemorrhoids.

What is the most common cause of occult blood in stool?

The most common causes of occult blood in stool include benign or malignant growths (polyps or cancer), haemorrhoids, ulcers, diverticular disease, and inflammatory conditions of the bowel.

Can a faecal occult blood test detect cancer?

A faecal occult blood test is used as a screening tool for colorectal cancer. While it can detect hidden blood that may be caused by cancer, it cannot diagnose cancer directly. A positive result requires further testing to confirm the diagnosis.

Can occult blood be cured?

Occult blood itself is a symptom, not a disease. Treatment depends on the underlying cause. Once the cause – such as polyps, ulcers, or haemorrhoids – is identified and treated, the bleeding (and thus the occult blood) can often be resolved.

Can faecal occult blood tests detect all colorectal cancers?

While FOBT is an effective screening tool, it may not detect all colorectal cancers or polyps, particularly those located higher in the colon. Follow-up testing, such as colonoscopy, may be recommended based on the results of FOBT or other clinical factors.

Are there alternatives to the faecal occult blood test for colorectal cancer screening?

Several alternative screening tests are available for colorectal cancer screening, including colonoscopy, sigmoidoscopy, and stool DNA testing. Your doctor can help determine the most appropriate screening approach based on your individual risk factors and preferences.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.