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What You Need to Know About At-Home Colorectal Cancer Screenings

There are caveats, but home test options exist for those squeamish about colonoscopy procedures.

So you’ve reached that point in life when your doctor has recommended colorectal cancer screening, but you just can’t cozy up to the idea of a colonoscopy.

Relax, you have options.

The good news is that there are home tests that doctors recommend to certain “average risk” patients. These stool tests are mailed to your home and contain instructions and materials to take a small sample and send it to a laboratory for testing.

How to Determine Your Eligibility

A patient is considered “average risk” for colorectal cancer if they don’t have a family history of colon cancer (a first-degree relative diagnosed under age 60), have never personally had precancerous polyps, and don’t have any diseases that predispose them to colon cancer, such as inflammatory bowel disease (IBD) or primary sclerosing cholangitis (a disease of the bile ducts).

“We do prefer the colonoscopy,” warns Dr. Hanisha Manickavasagan, gastroenterologist and IBD specialist. “Because it’s not only a screening test, but can prevent colon cancer. During your colonoscopy, your gastroenterologist will remove precancerous polyps (which are abnormal growths in the colon) that have the potential to turn into colon cancer over time.”

That said, Dr. Manickavasagan advises that there are mainly three home tests that serve as alternatives to colonoscopy: Guaiac Fecal Occult Blood Test (FOBT), Fecal Immunochemical Test (FIT or iFBOT) and Stool FIT-DNA.

Guaiac Fecal Occult Blood Test (FOBT)

The first option is the guaiac fecal occult blood test (FOBT), which is a noninvasive test for adults 45 and older at average risk for colon cancer. The FOBT is used to find occult blood (or blood that can’t be seen with the naked eye) in stool. The idea behind this test is that blood vessels at the surface of larger polyps or cancers are often fragile and easily damaged by passing stool. The damaged blood vessels usually release a microscopic amount of blood into the stool that may not be visible to the naked eye. The FOBT tests for peroxidase activity and is an easy way to determine whether there is blood in your stool, which could be the result of polyps or colorectal cancer. “It has a high sensitivity for blood, but not a high specificity for colon cancer,” Dr. Manickavasagan says. “Meaning you can get a false positive test if you are taking certain medications or eat red meat and certain vegetables.”

The FOBT detects blood in the stool through a chemical reaction. However, it can’t tell if the blood is from the colon, rectum, or from other parts of the digestive tract, like the stomach – or if it’s even human blood or animal blood. If this test is positive, your gastroenterologist will need to perform a colonoscopy to find the cause of bleeding. Although cancers and polyps can cause blood in the stool, there are other causes too. Ulcers, hemorrhoids, diverticulosis (tiny pouches that form at weak spots in the colon wall) or inflammatory bowel disease (colitis) may also cause blood in your stool.

This screening test is done with a kit that you can use in the privacy of your own home. Another important part of this kit and test is that it requires you to check more than one stool sample at a time, usually three. “The stool guaiac FOBT test also has to be repeated every year,” Dr. Manickavasagan notes, “compared to a colonoscopy which, for many people, only has be performed every five to ten years.”

Fecal Immunochemical Test (FIT)

The second option is a fecal immunochemical test (FIT), also called an immunochemical fecal occult blood test (iFOBT). It is a newer kind of stool test that also detects occult (hidden) blood in the stool. “However, it detects only human blood and thus has a much higher specificity for detecting precancerous polyps or colorectal cancer than the guaiac FOBT” Dr. Manickavasagan says.

The FIT is done essentially the same way as the traditional guaiac FOBT with a home stool kit, though some people may find it easier since there are no drug or dietary restrictions. Since vitamins and foods do not affect the FIT, sample collection may take less preparation. There are many varieties of FIT tests with varying levels of sensitivity, and depending on which one you have, it may require as few as one stool sample, instead of three, like a guaiac FOBT. However, the FIT test must also be repeated every year to achieve the best results of detecting colon cancer.

Stool FIT-DNA Test

The third option is the stool FIT-DNA test, which detects microscopic amounts of blood in stool through a FIT test, and 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. The test is also done at home by collecting a stool sample and shipping it to a laboratory for analysis – and should be repeated every three years.

Additional Options

Other options for colon cancer screening include flexible sigmoidoscopy, or flex sig, a procedure used to see inside the sigmoid colon (the last one-third of the colon) and rectum (which connects the sigmoid colon to the anus), and Computer Tomographic (CT) Colonography, also known as virtual colonoscopy, which is used to find polyps, cancer and other diseases of the large intestine through computerized technology.

Most home tests are covered by insurance. However, Dr. Manickavasagan notes, there is an important caveat to keep in mind. “If you opt to do the stool test instead of a screening colonoscopy, and the stool test comes back positive, you will now need a diagnostic colonoscopy to determine the source of bleeding. This is no longer considered a screening colonoscopy. The difference is that the screening colonoscopy is usually better covered by insurance – sometimes free, sometimes very low cost – whereas the diagnostic many times is not.”

Colorectal cancer screening should be a part of routine health care once you reach a certain age – or sooner if you have certain health conditions. Dr. Manickavasagan recommends talking to your doctor or a gastroenterologist to help decide which kind of colorectal cancer screening test is right for you.

“It will really depend on your risk factors and knowing your family history,” she says. “If there’s any family history of colon cancer or if you’ve previously had precancerous polyps, then I strongly recommend a colonoscopy rather than one of the home screening tests. Ultimately, any colon cancer screening test is certainly better than none.”

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From the Experts, Healthy You