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The U.S. Preventive Services Task Force recommends colorectal cancer screening for all adults starting at age 45. After age 75, the task force recommends talking with your health care team to decide if you still need screenings. If you are at high risk for colon cancer, you may need to start screenings before age 45 or have them more often.
The fecal immunochemical test (FIT) and guaiac-based fecal occult blood test (gFOBT) are at-home screening tests for colon cancer. Another at-home screening test is called Cologuard. An additional screening option is getting a colonoscopy.
Schedule Your Screening
Talk to your primary care provider about colorectal cancer screening. UW Medicine Primary Care can help you get started with screening. Learn about Fred Hutch's relationship with UW Medicine.
Fecal Immunochemical Tests (FIT)
FIT is a colon cancer screening test you can do at home. It comes in a kit and is fairly quick, simple and convenient to use. FIT is a noninvasive, stool-based test. You use the kit to take a sample of your stool. Then you send the sample to a lab for testing. Your primary care provider can give you a FIT kit or have one mailed to you.
Fred Hutch Cancer Center is studying ways to increase colon cancer screening rates by mailing FIT kits. The Population Health Colorectal Cancer Program is working to understand barriers people might face and how health care providers can support people in getting screened.
How FIT Helps Diagnose Colon Cancer
The FIT checks for blood in the stool using antibodies. Polyps or cancer may bleed, but they may not release enough blood for you to notice. It may be only a very small amount that you can’t see. FIT can detect this hidden (occult) blood. More precisely, it can detect the hemoglobin protein in blood.
If the test finds blood, you will need a colonoscopy to find out why. It may not be from polyps or cancer. Other conditions, like hemorrhoids, can also lead to a positive test result (finding of blood). The blood may not even be from your colon. It could be from another part of your digestive system. That’s why additional tests are needed.
If the FIT doesn’t find any blood, the usual schedule is to repeat the test once a year to check again.
How to Prepare for a FIT Test and What to Expect from the Test
You don’t need to do anything special to prepare for a FIT test. You don’t need to change your diet or medicines or do bowel prep (steps to clean out your colon), like for a colonoscopy.
When you’re ready to use your kit, open it up and follow the instructions step by step. The kit contains the supplies you will need. You will use a small stick or brush to collect one sample of stool and then seal it in a container. The kit includes an envelope so you can send your sample to the lab. Typically, the kit says to send the sample within 24 hours after you collect it.
If you have questions about using your kit, call your primary care provider (or other member of your health care team who arranged the test for you). Your provider will let you know when the results are back.
You can find FIT instructional videos on the Fred Hutch Population Health Colorectal Cancer Screening Program page.
Guaiac-based Fecal Occult Blood Test (gFOBT)
Like FIT, gFOBT is an at-home, stool-based screening test for colon cancer. It requires you to collect samples from three bowel movements, rather than only one. But it’s still fairly quick, like FIT, and easy to do. Your primary care provider can give you a gFOBT kit or have one mailed to you.
How gFOBT Helps Diagnose Colon Cancer
gFOBT uses a chemical called guaiac to tell if there’s heme in your stool. Heme is part of hemoglobin, a protein in blood. Heme can be in your stool if you’re not bleeding but you’ve eaten meat recently. So, part of the preparation for gFOBT is to avoid certain foods for a few days.
How to Prepare for a gFOBT Test and What to Expect from the Test
Your health care team will give you details about how to prepare. Usually, patients are told to avoid taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen or aspirin, for a week before the test. These medicines can cause bleeding, which might skew your test results. If you take NSAIDs regularly, ask your care team before stopping them.
You may also be told to make these diet changes:
- Stop taking vitamin C supplements, and avoid fruits or juices with vitamin C for up to a week before the test.
- Avoid eating beef, liver or lamb for three days before the test.
You don’t need to do any bowel prep.
When you’re ready to use your kit, open it up and follow the instructions step by step. The kit contains the supplies you will need. You will use a small stick or brush to collect a sample of stool. Usually, the next step is to smear the sample on a small test card. The kit includes an envelope so you can send your samples to a lab, or you might be told to return it to your provider’s clinic.
If you have questions about using your kit, call your primary care provider (or other member of your health care team who arranged the test for you). Your provider will let you know when the results are back.
If the test finds blood, you will need a colonoscopy to find out why. If the test doesn’t find any blood, the usual recommendation is to repeat the test once a year to see if anything has changed.
Using the tests is not risky. Both involve taking a sample of your own stool, which you might find unpleasant. Like with all tests, there is some chance of a false negative (not finding blood even though it’s there) or a false positive (finding that there’s blood when there really isn’t).
Some of the key differences between stool tests and colonoscopy are:
- You can do stool tests at home. You don’t have to go to a clinic or office. You do have to take samples of your own stool and return them.
- You don’t need to do bowel prep before stool tests.
- You don’t need to be sedated for stool tests.
- Stool tests are not invasive. Testing tools are not put in your body.
- Even if the results are negative (no problem detected), you need to repeat a FIT or gFOBT test every year (versus every 10 years for colonoscopy).
- If a FIT or gFOBT detects blood, you need to have a follow-up colonoscopy.
- FIT or gFOBT alone doesn’t let your physician remove polyps or abnormal tissue to prevent or diagnose colon cancer.