Everything about at-home colorectal cancer tests: Accuracy, benefits and when you still need a colonoscopy

Colorectal cancer is the second most common cause of cancer death, and you may not develop symptoms until it's more advanced. Thankfully, it's often preventable with colorectal cancer screening.

The American Cancer Society (ACS) 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.

"Studies have shown that the survival rate for people diagnosed with colorectal cancer in its early stages is more than 90%, and many cancers can be prevented altogether," says Robert B. Noone Jr., MD, colon and rectal surgeon at Main Line Health. "Yet one in three adults do not get tested. Colorectal cancer is now the top cancer killer of adults under the age of 50, so getting screened is even more critical."

Finding polyps or colorectal cancer through at-home cancer tests without a colonoscopy

While the gold standard is colonoscopy, home-based screenings are also an option for some people at average risk. "If you're hesitant about having a colonoscopy, a home-based test is better than no test at all," says Dr. Noone.

As with most medical care, your first step should be to discuss your options with your personal clinician. "It's important to talk to your doctor about which test is right for you and how often you should be screened," Dr. Noone explains.

What happens if an at-home colorectal cancer test is positive?

Dr. Noone notes that a positive result on a home colorectal cancer test will require a follow up with a colonoscopy performed by a health care professional.

Aside from that important inquiry, what else do you need to know about at-home colorectal cancer tests? Dr. Noone answers our most frequently asked questions below.

What home colorectal cancer test options are available?

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

• Guaiac fecal occult blood test (gFOBT) – Checks for hidden blood in the stool with a chemical called guaiac
• Fecal immunochemical test (FIT) – Uses antibodies to check for hidden blood in stool
• FIT-DNA stool test (Cologuard®) – Combines the FIT with a test that checks DNA in stool cells for genetic changes that may be a sign of colorectal cancer
• FIT-RNA stool test (ColoSense®) – Looks for genetic biomarkers associated with colorectal cancer and precancerous polyps

How accurate are home colorectal cancer tests?

FIT tests are typically more accurate than gFOBT tests, and FIT-DNA and RNA tests are the most accurate, at around 92 percent.

"Although these at-home tests are fairly reliable, 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," says Dr. Noone. "Any positive result will be followed up with a colonoscopy."

How do you collect a sample?

gFOBT cancer testing

• Where to get it: You'll receive a test kit from your health care provider.
• How to use it: 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.
• Additional considerations: You'll have some dietary restrictions and will collect stool samples for three consecutive days.

FIT cancer testing

• Where to get it: You'll receive a test kit from your health care provider.
• How to use it: 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.
• Additional considerations: There are no dietary restrictions, and you'll need only one sample.

FIT-DNA or RNA cancer testing

• Where to get it: You'll receive a test kit from your health care provider.
• How to use it: At home, you collect an entire bowel movement and send it to a lab, where it's checked for altered DNA or RNA biomarkers, and for the presence of blood.
• Additional considerations: 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 and RNA tests should be repeated every three years.

Comparatively, a colonoscopy screening can be done every 10 years or more frequently depending on what is found and your risk factors.

Is there a blood test for colon cancer?

Blood-based tests are another option for colorectal cancer screening, but they are not currently considered a first-choice screening option. A blood-based test can detect signs of colorectal cancer, but it is less effective at finding precancerous growths and early-stage cancers than stool-based screening tests and colonoscopy.

"Blood-based tests should only be considered as a last resort for someone who is unwilling or unable to complete a stool-based test or colonoscopy," says Dr. Noone.

What about genetic testing for cancer?

Genetic counseling and testing is available and may be recommended if someone in your family has colorectal cancer. As colorectal cancers are linked to other cancers by the same genes (such as with Lynch syndrome), you may also want to consider genetic counseling if a family member had a different type of cancer. If you're not sure if cancer runs in your family, an evaluation by a genetic counselor could help you determine your personal risk and if you should be tested.

What are the benefits and limits 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
• Noninvasive
• Can be done at home
• Able to be completed without special needs for bowel preparation

Stool-based testing is most beneficial when done over time. "Stool-based tests are not as sensitive as colonoscopy; meaning they may miss some polyps or cancer or give a false positive (detecting cancer when it's not there). Plus, any positive results on stool-based or blood-based screening tests require follow-up with colonoscopy," says Dr. Noone.

He continues with, "While there are many types of colorectal cancer screening tests, colonoscopy is the only test that can find and remove precancerous polyps 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 cancer test. Colonoscopies are performed by a gastroenterologist or colorectal surgeon.

Can AI chatbots like ChatGPT or other LLM tools explain my at-home cancer screening test results?

No, not reliably. While AI chatbots and LLMs can explain medical test results in simpler terms, they also may provide outdated, inaccurate or overly generalized information. If you have questions about an at-home colorectal cancer screening test, talk with your primary care provider or gastroenterologist. They can interpret the results in the context of your personal health history and give clear guidelines on tailored next steps.

For more information about safely using AI chatbots for health questions, review the American Medical Association's infographic.

Is colorectal cancer screening covered by insurance?

Colorectal cancer screening is typically 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 Robert B. Noone Jr., MD.

Learn more about colorectal cancer care at Main Line Health.

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