Blood in the stool is a manifestation of gastrointestinal tract damage, including: tumors, polyps, bleeding, diverticular disease, colorectal cancer, etc. Blood present in the stool may not be visible to the naked eye when the amount is very small. Therefore, testing for hidden blood in the stool helps to detect this.
1. Two methods for testing hidden blood in the stool
There are two main methods for testing hidden blood in the stool used in laboratories, including:
- Guaiac fecal occult blood test (gFOBT): This test requires the patient to collect 2-3 stool samples and may require dietary changes and medication adjustments (discontinuing anti-inflammatory, non-steroidal drugs 7 days prior to sample collection; avoiding broccoli, radishes, red meat, and vitamin C doses over 250mg per day for 3 days).
- Immunochemical fecal occult blood test (Fit): This test is often more widely used due to its numerous advantages over gFOBT, including higher sensitivity. It does not require any dietary restrictions before collecting the samples and can be performed on a random stool sample.
2. What is the test for hidden blood in the stool?
The hidden blood test (also known as occult red blood) in the stool (fecal occult blood) aims to detect very small amounts of blood in the stool sample that are not visible to the naked eye.
Blood in the stool indicates a gastrointestinal tract injury. It can be caused by many factors, including: polyps, colitis, gastrointestinal bleeding, tumors, diverticular disease…
Blood in the stool can also be a sign of colorectal cancer (colorectal cancer is the second leading cause of cancer deaths in the U.S. and is the third most common cancer in both men and women). Therefore, screening for hidden blood in the stool can help detect colorectal cancer early and treat it effectively.
3. What is the purpose of testing for hidden blood in the stool?
- Screening for colorectal cancer.
- Diagnosing conditions that cause gastrointestinal bleeding.
4. Who needs to be tested for hidden blood in the stool?
The American Cancer Society recommends screening for colorectal cancer for individuals aged 45-75. The Coalition for Colorectal Cancer Coalition recommends starting screening at age 50 and earlier for those at high risk.
Testing for hidden blood in the stool should be done periodically every year.
5. What should be done next upon receiving the results of the hidden blood in stool test?
If the result is negative, it means no blood was detected in the stool at the time of testing. However, this does not mean that there is no colorectal cancer (in cases where the tumor is not bleeding). The individual should continue to undergo annual testing for hidden blood in the stool.
If the positive result means there is damage somewhere in the digestive tract, it does not mean colorectal cancer. The doctor needs to request additional tests, for example, a colonoscopy to detect the location of the bleeding.
