Do at-home colon cancer tests work?

The preparation for colonoscopy, the exam that helps prevent colorectal cancer, is famously unpleasant. It’s no wonder that many people opt for a simpler, noninvasive alternative that doesn’t require fasting or a hospital procedure: the at-home colorectal cancer test.

“These tests are intended for patients who are at average risk and prefer to avoid the invasiveness of colonoscopy,” says Dr. William Karnes, a gastroenterologist at the UCI Health Chao Digestive Health Institute.

Here are the basic test types:

• Fecal immunochemical test (FIT), which detects human hemoglobin in a stool sample collected at home and sent in for testing. It is the most popular option for patents.
• Multitarget stool DNA test (MTsDNA), which combines the FIT hemoglobin detection with a search for DNA markers. This option has higher sensitivity for detecting colorectal cancer and advanced adenomas compared with FIT alone.
• Guaiac fecal occult blood test (gFOBT), which detects peroxidase activity in hemoglobin in a stool sample. Dietary restrictions, longer fasting time and reduced sensitivity and specificity make this option less popular.

While convenient, each of these tests do have some limitations. Colonoscopy with removal of polyps can prevent most colorectal cancers, whereas these noninvasive tests do not prevent colorectal cancer directly but can help find colorectal cancer at early curable stages..

What to do with a positive result

While the benefit of such at-home tests is avoiding a trip to the hospital for a procedure if the result is negative. However, you will still need to get a colonoscopy to rule out cancer if the result is positive, Karnes says.

The chances of a positive test being colorectal cancer are between 1.3% and 3.4%, he says. However, the rate of false positives for these at-home tests ranges from 5% to 10%, which means scheduling a colonoscopy.

“It is crucial to follow up a positive result with a colonoscopy for definitive diagnosis and management,” ideally within three to six months, Karnes says.

Simply repeating the test is not enough.

“The American College of Surgeons states that repeating a positivity stool-based test to determine whether to proceed to a colonoscopy is not an appropriate strategy,” he says.

Not ideal for everyone

At-home stool-based tests are appropriate for “average-risk” individuals and are not appropriate for individuals with:

• A family history of colorectal cancer
• Predisposing hereditary syndromes, such as Lynch syndrome
• Inflammatory bowel disease
• A history of precancerous polyps
• Any concerning symptoms such as rectal bleeding or thinning of the stools

Anyone at increased risk for polyps should skip the at-home and go straight for a colonoscopy, Karnes recommends. Colonoscopy is far more accurate than any noninvasive test at detecting polyps, particularly advanced ones. During the procedure, such polyps are removed and biopsied immediately.

“Average-risk individuals can choose between colonoscopy and at-home tests based on personal preference and test availability,” Karnes says.

Limitations of home tests

While at-home colorectal cancer tests can detect signs of colorectal cancer, unlike colonoscopies, they cannot identify the presence of polyps let alone remove them to prevent their progression to cancer.

Even so, at-home tests have become important tools in the fight to eradicate colorectal cancer. The American College of Gastroenterology supports the use of such tests as part of a comprehensive screening strategy.

“They play a crucial role in early detection, which can lead to preventive measures thereby reducing the incidence and mortality of colorectal cancer,” Karnes says.