Why is a FOBT performed?
FOBT is most commonly performed as a screening test for colon cancer and rectal cancer. If you don’t have any risk factors for colorectal cancer, including a family history of colon cancer or symptoms, this test may be an option for you starting at age 45. FOBT can also be used when you have signs of a digestive condition.
Your doctor might order a FOBT if you have digestive symptoms or anemia—a condition in which you have a low red blood cell count. This test can help uncover hidden bleeding in the digestive tract so that your doctor can recommend your next steps.
Understanding the results
Fecal occult blood tests can only detect the presence of blood in the stool—and, depending on the test, DNA markers. While they are helpful tools for your health and peace of mind, it’s important to understand that these tests can’t diagnose or confirm a condition. Be sure to talk to your doctor about what your results mean for you and your next steps.
- Negative result: A negative result means no signs of hidden blood (or DNA markers if taking a stool DNA test) were found in the stool. For colorectal screening, you’ll follow the guidelines for your next test every year or three years.
- Positive result: A positive result means that blood or DNA markers were detected on your test. This could be caused by many conditions and does not mean you have colorectal cancer. You may have follow-up testing with a colonoscopy to find the cause behind the bleeding or markers.
- False-negative results: Although the performance of these tests is highly dependable, FOBTs are not 100% accurate and can miss polyps, and sometimes signs of cancer, when compared to a colonoscopy.
- False positive results: The test coming back positive doesn’t necessarily mean you have colon cancer or polyps. These tests can send a false signal up to 50% of the time.