Fecal Occult Blood Test (FOBT)

The Fecal Occult Blood Test (FOBT) checks for hidden (occult) blood in the stool. Occult blood may not be visible to the naked eye but can be an early sign of colorectal cancer, polyps, ulcers, or gastrointestinal bleeding. This test is often used as a screening tool for colon cancer and other digestive system disorders.

1. What Is Occult Blood?

• Occult blood refers to small amounts of blood that are not visible but can be detected chemically.

• It may originate from anywhere in the gastrointestinal (GI) tract, including the stomach, small intestine, or colon.

• Persistent presence of occult blood may warrant further investigation, such as a colonoscopy.

2. Why Is the FOBT Performed?

This test is used to:

• Screen for colorectal cancer or precancerous polyps.

• Investigate causes of unexplained anemia or GI symptoms (e.g., abdominal pain, changes in bowel habits).

• Detect ulcers, diverticulosis, or inflammatory bowel disease (IBD).

3. Types of Fecal Occult Blood Tests

• Guaiac-based FOBT (gFOBT):

  - Uses a chemical reaction to detect heme in blood.

  - Requires dietary restrictions to avoid false positives (e.g., red meat, certain vegetables, vitamin C).

• Fecal Immunochemical Test (FIT):

  - Uses antibodies to detect human hemoglobin protein in stool.

  - More specific to lower GI bleeding; no dietary restrictions required.

4. How to Interpret FOBT Results

🔹 Positive Result:

• Indicates blood is present in the stool.

• May require follow-up with colonoscopy or other diagnostic tests.

🔹 Negative Result:

• No occult blood detected at the time of testing.

• Does not completely rule out GI conditions—testing may need to be repeated annually for screening.

5. What Can Affect FOBT Accuracy?

• Diet (for gFOBT): red meat, raw fruits and vegetables, and vitamin C can interfere with results.

• Medications: NSAIDs or aspirin may increase risk of GI bleeding and false positives.

• Timing: Blood from hemorrhoids or menstruation can contaminate the sample.

6. How Is the Test Performed?

• The test is usually performed at home using a test kit provided by your healthcare provider.

• A small stool sample is collected using a special applicator and applied to a test card or placed in a sample container.

• The sample is returned to a lab or clinic for analysis.

7. When to See a Doctor

🚨 Contact your healthcare provider if you:

• Have a positive FOBT result.

• Experience symptoms such as rectal bleeding, persistent abdominal pain, or unexplained weight loss.

• Have a family history of colorectal cancer or polyps.

🔹 Key Takeaways

✅ FOBT is a non-invasive test used to detect hidden blood in the stool, often for colon cancer screening.

✅ Positive results may indicate bleeding in the GI tract and require follow-up testing.

✅ Annual screening with FIT or gFOBT is recommended for adults over age 50 (or earlier for those at higher risk).