Colorectal Cancer Screening: Testing for Blood in Your Stool

There are 3 main types of fecal occult blood tests (FOBT). Occult blood means blood is not visible with the naked eye. They include:

• Guaiac fecal occult blood test (gFOBT). This uses a chemical to find blood in your stool This test is done once a year.
• Fecal immunochemical test (FIT). This test uses anitbodies to detect blood in the stool. This test is done once a year.
• FIT-DNA test. (also referred to as the stool DNA test. This test combines the FIT test for blood with a test that also detects altered DNA in the stool. This test is done once every 3 years.

Before you get started, here are some things to know.

• These screening tests don’t diagnose cancer. They look for blood and or altered DNA in your digestive tract.
• If the test finds blood in your stool, it doesn’t mean that you have cancer. It could mean that you have polyps, hemorrhoids, ulcers, diverticulosis, or inflammatory bowel disease. Talk with your healthcare provider after your results to know for sure.
• It’s possible to have false positives and false negatives. A false positive is when the test shows the possibility of a polyp or cancer when it’s not there. A false negative is when the test doesn’t detect blood but cancer or a polyp is present but doesn't bleed.
• If your result is positive, you will need a colonoscopy procedure that closely examines the cause of the bleeding. Talk with your provider about next steps. They can help you schedule a colonoscopy.

Fortunately , you don’t need to go to a lab to get these tests done. They’re easy to do on your own from home. Your healthcare provider can give you a test kit and any additional information you may need. While these tests are simple, know that they do involve collecting some of your own stool (poop).

Each test has different instructions, so it's very important to follow them exactly for accurate results. When you’re about to do the test, check that you have all your supplies nearby in the bathroom.

You may need to collect 1 to 3 separate stool samples depending on the type of test. You can gather the stool using a clean container or by draping plastic wrap loosely across your toilet bowl to catch it. Then, use the provided applicator to spread the sample onto the testing kits before sending them as instructed.

FIT

If you’re using the FIT, or FIT-DNA tests there aren’t any dietary or medicine restrictions for taking the test. Medicines and foods don’t affect this test.

gFOBT

You need to pay close attention to your eating and other habits if you’re using the gFOBT. Don’t forget that it’s very important to follow the prep instructions in your kit to make sure you get the correct results.

All test kits come with detailed instructions. But certain foods and medicines can affect the results of gFOBT tests. So you might see these general guidelines:

• Don't eat red meat (beef, liver, or lamb) for 3 days before the test.
• Don't have more than 250 mg of vitamin C a day (either from supplements or citrus fruits and juices) for 3 to 7 days before the test.
• Don't use products that contain aspirin or use nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, for 7 days before the test.

Always read the prep kit thoroughly before you test. If you have questions, talk with your healthcare provider. They’re there to help you through the testing process so you’re comfortable doing it at home.