Can a Home DNA Stool Test Replace a Colonoscopy?
There's no scope and no prep necessary — so is it too good to be true?
You’re not looking forward to your first, or next, colonoscopy (though really, colonoscopies aren’t as bad as they seem), so you’re exploring other screening options. There are several other tests designed to catch colon cancer early. Among the newest is a stool DNA test called Cologuard, approved by the FDA in 2014. You don’t even have to leave home to take it.
If you’re considering it, here’s the poop on what the test can and can't do.
How the DNA stool test works
Cologuard relies on a stool sample you collect at home. Your doctor has to order the test, and then the company ships you a kit with instructions. You don't need to follow any special dietary restrictions or stop any medicines before taking it, according to the company.
The test detects mutations in DNA of cells shed as the stool moves though the bowels. These abnormalities may signal cancers or ''pre-cancers." It also looks for blood in stool.
Once you collect the sample, you ship it back to the company for analysis. Those results are sent to your doctor within two weeks, the company says. Your doctor will contact you to discuss the results.
One catch: Cologaurd is only for people at average risk of colon cancer. If you have a history of pre-cancerous growths known as polyps, colon cancer or other colon ailments, you aren't a candidate. Your doctor can decide by reviewing your history if you’re at average or above-average risk.
According to the manufacturer, you also shouldn’t use the test if you have bleeding hemorrhoids, since the blood could interfere with the results. It shouldn't be taken during menstruation for the same reason.
The American Cancer Society, which lays out the different colon cancer screening options here, says, “If you’re 50 or older, talk to your doctor about which test is right for you and get tested as often as recommended.”
How accurate is the test?
In trials, the DNA stool test found 92 percent of cancers in 10,000 people, according to the company and the FDA. It gave a negative result for 87 percent of people who were cancer-free. (The others got a ''false positive,'' a possibility with all tests.)
When the FDA compared the stool test with the fecal immunochemical test or FIT (another colon screening test, which detects blood in the stool), it found Cologuard detected cancer and advanced adenomas (non-cancerous large polyps or growths that could progress to cancer) more often than FIT. While Cologuard found 92 percent of cancers, FIT found only 74 percent. Cologuard found 42 percent of advanced adenomas and FIT detected 24 percent, the FDA said.
This year, more than 134,000 cases of colorectal cancer will be diagnosed, according to estimates from the American Cancer Society.
What if it's positive? Negative?
If the Cologuard result is positive, your doctor will advise you to have a colonoscopy to confirm those results. If the result is negative, your doctor will advise you on what, if anything, to do next.
Cologuard does not have any data yet on how well a repeat test works. So if your initial test is negative, your doctor will advise you whether to take it again for your next screening or switch to another test.
Related: Take Good Care Of Your Colon
What's the cost, who pays?
According to the company, the maximum cost is $649. However, many insurance plans now cover it, though you may need to pay a co-pay and/or or meet your deductible.
The test is covered under Medicare. Depending on the Medicare plan, some patients may have co-pays or deductibles to pay.
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