Everything you always wanted to know about home colorectal cancer tests but were afraid to ask

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Colorectal cancer is almost entirely preventable with a colorectal cancer screening. The American Cancer Society recommends that adults begin colorectal cancer screening at age 45. Your doctor may recommend beginning screening earlier if you're at increased risk for colorectal cancer based on factors such as your personal and family history of colorectal cancer or colon polyps that can become cancer. 

Several screening tests can be used to find polyps or colorectal cancer.

"While the gold standard is colonoscopy, home-based screenings are also an option for some people at average risk," says Malini Mathur, MD, gastroenterologist at Lankenau Medical Center, part of Main Line Health. "If you're hesitant about having a colonoscopy, a home-based test is better than no test at all. It's important to talk to your doctor about which test is right for you and how often you should be screened."

Dr. Mathur notes that a positive result on a home colorectal cancer test will be followed up with colonoscopy. So, what do you need to know about at-home tests? Read on for answers to our most frequently asked questions.

What home colorectal cancer test options are available?

Home stool-based tests look for signs of cancer in a person's stool. There are three types of tests:

  • A guaiac fecal occult blood test (gFOBT) checks for hidden blood in the stool with a chemical called guaiac.
  • A fecal immunochemical test (FIT) uses antibodies to check for hidden blood in the stool.
  • A FIT-DNA stool test (e.g., Cologuard®) combines the FIT with a test that checks DNA in stool cells for genetic changes that may be a sign of colorectal cancer.

How accurate are these home colorectal cancer tests?

FIT tests are generally more accurate than gFOBT tests, and FIT-DNA tests are the most accurate, at around 92 percent. Still, all can produce false-negative results, meaning they do not detect cancer when it's there, or false-positive results, meaning they detect cancer when none is there. Any positive result will be followed up with a colonoscopy. 

How do you collect a sample?

  • With a gFOBT test, you receive a test kit from your health care provider. At home, you use a stick or brush to obtain a small amount of stool, which you place on a special card and return to a doctor or laboratory for testing. You'll have some dietary restrictions and will collect stool samples for three consecutive days.
  • With a FIT test, you receive a test kit from your health care provider. At home, you use a stick or brush to obtain a small amount of stool, which is placed in a special collection tube or on special cards and returned to a doctor or laboratory for testing. There are no dietary restrictions, and you'll need only one sample.
  • With a FIT-DNA test, you receive a test kit from your health care provider. At home, you collect an entire bowel movement and send it to a lab, where it's checked for altered DNA and for the presence of blood. There are no dietary restrictions, and you'll need only one sample.

How often should you do a home test?

FIT and gFOBT tests should be repeated every year. FIT-DNA tests should be repeated every three years.

Comparatively, a colonoscopy screening can be every 10 years or more frequently depending on what is found and the patient's risk factors.

What are the benefits and drawbacks of home tests?

Stool-based screenings require people to collect samples directly from their feces, which may be unpleasant for some, but the test is quick and noninvasive and can be done at home, and no bowel preparation is needed. Stool-based testing is most beneficial when done over time.

Stool-based tests are not as accurate as colonoscopy, and any positive results on stool-based screening tests require follow-up with colonoscopy. While there are many types of colorectal cancer screening tests, colonoscopy is the only test that can find precancerous polyps and remove them before they become cancerous.

Do I need a prescription from my doctor?

Yes, you will need a prescription from your primary care provider or gastroenterologist for any at-home test. Colonoscopies are performed by a gastroenterologist or colorectal surgeon.

Is colorectal cancer screening covered by insurance?

All colorectal cancer screening is generally covered by insurance at regular intervals, but it's best to check with your insurance provider to be sure.

Next steps:

Make an appointment with Malini Mathur, MD
Learn more about colorectal cancer care at Main Line Health 
Do you know when to get these cancer screenings?