There are three at-home tests that check for blood in your stool:
The fecal immunochemical test (FIT) uses antibodies to find blood in stool. Research shows that FIT testing is better at finding colorectal cancers than FOBT testing. A FIT test requires stool samples from one to three separate bowel movements, depending on the brand of the test.
The fecal occult blood test (FOBT) uses a chemical (guaiac) to find blood in stool. It usually requires stool samples from two or three separate bowel movements.
You can buy FOBT and FIT stool collection kits without a prescription. Most of these tests require you to send a sample of your stool to a lab. But some tests can be done completely at home for quick results. If you’re considering buying your own test, ask your provider which one is best for you.
A third screening option is the stool DNA test, which is a noninvasive test for adults 45 and older at average risk for colon cancer. Like the fecal occult blood test, the stool DNA Test detects microscopic amounts of blood in stool, but it also looks for certain DNA changes and mutations found in cancerous tumors or precancerous polyps. A stool DNA test requires a prescription and then the test kit is mailed to your home.
- The fecal immunochemical test (FIT)
- The fecal occult blood test (FOBT)
- Stool DNA test
Fecal Immunochemical Test (FIT)
FIT is a non-invasive test that checks for blood in your stool and is typically recommended every year starting at age 50, or earlier for those with a family history or other risk factors. There are no special preparations required for the test. After having a bowel movement at home, you swipe your stool with a brush included in the kit, then touch the brush to the space indicated on the test card and send it to the lab for testing.
A normal result means the test did not detect any blood in the stool. However, because cancers in the colon may not always bleed, you may need to do the test a few times to confirm that there is no blood in your stool.
If the FIT results come back positive for blood in the stool, your doctor will want to perform other tests, usually including a colonoscopy. The FIT test does not diagnose cancer. Screening tests such as a sigmoidoscopy or colonoscopy visually inspect the colon and are much better at detecting cancer.
Fecal Occult Blood Test (FOBT)
FOBT is another test that checks for blood in the stool. Occult means it cannot be seen with the naked eye. It is also non-invasive and typically recommended every year starting at age 50, or earlier for those with a family history or other risk factors. It is less sensitive than FIT and may require multiple samples.
Before using a FOBT, you may need to avoid certain foods and medicines that may affect the results of the test including nonsteroidal, anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, and aspirin, Vitamin C, and red meat, because traces of blood from these meats may show up in your stool.
After having a bowel movement at home, you swipe your stool with a brush included in the kit, then either smear the stool on a special test card or insert the applicator with the stool sample into a tube that came with your kit and mail it into the lab as directed.
If your results from a fecal occult blood test show that you have blood in your stool, it means you likely have bleeding somewhere in your digestive tract. But that doesn’t always mean you have cancer. Other conditions that may cause blood in your stool include ulcers, hemorrhoids, polyps, and benign (not cancer) tumors.
If you have blood in your stool, your provider will likely recommend more tests to figure out the exact location and cause of your bleeding. The most common follow-up test is a colonoscopy.
Stool DNA test
A Stool DNA test is noninvasive and recommended for adults 45 and older at average risk for colon cancer. Like the fecal occult blood test, the stool DNA test detects microscopic amounts of blood in stool, but it also looks for certain DNA changes and mutations found in cancerous tumors or precancerous polyps. Cells from precancerous and cancerous lesions with these mutations often shed DNA biomarkers into the stool, where this test can detect them, therefore indicating the presence of precancerous polyps or colon cancer.
There is no prep required and there are no dietary restrictions or changes to medications necessary. After having a bowel movement at home, you’ll collect a stool sample utilizing the kit provided to you and mail it to the lab as directed.
If an at-home test is positive, it’s important to follow up with a doctor for further evaluation. The doctor may recommend a colonoscopy or a sigmoidoscopy, which are procedures that allow the doctor to examine the inside of the colon and rectum and take biopsies, as necessary.
CT colonography (Virtual Colonoscopy)
A virtual colonoscopy, or CT colonography, is a non-invasive test that uses X-rays to create detailed images of the colon. It does not require sedation like a colonoscopy, but it does require the colon to be cleaned out beforehand. CT colonography is typically recommended every 5 years starting at age 50, or earlier for those with a family history or other risk factors.
One downside to a virtual colonoscopy is the inability to take biopsies if abnormal tissue is identified.