What is the Stool Occult Blood Test (Stool Occult Blood Test)?
The Stool Occult Blood Test, or Stool Occult Blood Test (FOBT), is a screening test to detect small amounts of blood mixed in the stool that are not visible to the naked eye. This test helps identify abnormalities in the gastrointestinal tract and is one of the important methods for screening colorectal cancer from the early stages.
Why should you have a stool occult blood test?
This test is important because it helps detect abnormalities in the gastrointestinal tract before symptoms appear, especially colorectal cancer, which is one of the leading causes of death among Thais and is increasingly common. This test helps doctors diagnose diseases early and provide timely treatment.
Benefits of the test
- Screening for colorectal cancer and polyps
- Identify causes of anemia or iron deficiency
- Detect gastrointestinal bleeding
- Suitable for high-risk individuals such as
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- Age 45 years and older
- Family history of colorectal cancer
- Symptoms of mucus or blood in stool, black stool
- Chronic unexplained abdominal pain
Currently, there are 2 main methods used in hospitals for stool occult blood testing.
- Guaiac-based FOBT (gFOBT)
- Uses chemicals to react with hemoglobin in the stool
- Must avoid certain foods such as red meat, beetroot, and iron-rich vegetables
- May need to avoid some medications such as aspirin, NSAIDs, and vitamin C
- Immunochemical FOBT (iFOBT) or FIT
- Uses technology to detect antibodies specific to hemoglobin in the stool
- Highly accurate and does not require dietary or medication restrictions before testing
- Currently popular because it is convenient, fast, and reliable (Phayathai 2 Hospital uses this method for testing)
- An accurate method for colorectal cancer screening with sensitivity up to 79% and specificity up to 94%
Preparation before the test
- Avoid certain medications such as aspirin anticoagulants or NSAIDs (always consult a doctor first)
- Avoid iron-rich foods or red meat 2–3 days before the test if using the gFOBT method
- Postpone the test if menstruating to avoid false positive results
Interpretation of stool occult blood test results
Negative result
- No occult blood detected in the stool
- For the general population, it is recommended to repeat the test annually starting at age 45 and older
Positive result
- Occult blood detected in the stool
- Does not necessarily mean cancer. Further testing is required, such as colonoscopy to find the cause
Advantages of the test
- Easy to perform, painless, no preparation needed
- Helps screen diseases from the early stages
- Suitable for individuals at risk of colorectal cancer
Limitations of the test
- Cannot specify the exact location of bleeding
- May give false positive or false negative results
- If positive, further testing with other methods is necessary to find the cause
When should you have a stool occult blood test?
- Individuals aged 45 and older should have annual screening
- Those with a family history of colorectal cancer or previously found polyps in the colon
- Those with abnormal symptoms such as bloody stool black stool unexplained weight loss or chronic abdominal pain
The Stool Occult Blood Test (Stool Occult Blood Test) is a simple, safe, and highly effective screening method to detect abnormalities in the gastrointestinal tract, especially colorectal cancer. Early detection increases the chances of treatment and reduces the risk of severe disease in the future.
Dr. Natthida Sribuathong
Gastroenterologist and Hepatologist
Phayathai 2 Hospital
