COLOGUARD PROS AND CONS
December 9, 2021 - Nobody looks forward to a colonoscopy, and the manufacturer or Cologuard knows this. Cologuard commercials, which seem to run nonstop, promise an easy, at-home method for colon cancer screening that beats the heck out of messy preps and lying naked on a hospital bed in front of strangers for hours. But how good is Cologuard at detecting colon cancer, and what are the disadvantages? Your local gastroenterologist probably doesn't recommend it, but then again, he doesn't put his kids through college by telling you to skip the colonoscopy for Cologuard. So let's take an honest look at the test from a perspective that doesn't have any skin in the game.
First off, it's important to note that Cologuard is only for people at average risk for colon cancer. The test should not be used if someone has a history of polyps on a previous colonoscopy, a strong family history of colon cancer, or some other condition (e.g. inflammatory bowel disease) that increases their risk of colon cancer.
How does Cologuard work? When you send in a Cologuard sample, the manufacturer actually performs two tests - a fecal DNA test and a fecal immunochemical test (FIT). The fecal DNA test detects common genetic mutations in colon cancers that may be present in cells that are shed in the stool. The FIT detects blood in the stool. If either test is positive, the entire Cologuard result comes back positive, and the manufacturer does not specify which test caused the positive result. This is important because FITs are available over-the-counter and cost about $12, whereas Cologuard costs around $600. Someone could do a FIT first, and if that is positive, they could skip the Cologuard. Also, people who have hemorrhoids that bleed frequently should know that they are likely to get a positive Cologuard test.
How good is Cologuard at detecting colon cancer? Cologuard is about 92% effective at detecting colon cancer and 42% effective at detecting advanced precancerous polyps. The colon cancer detection rate is good, but 58% of precancerous lesions will go undetected; these lesions would likely be removed during a colonoscopy. Cologuard is recommended every 3 years, and a colonoscopy is recommended every 10 years. Over ten years, patients would be screened with one colonoscopy or three Cologuard tests. Cologuard has a false-positive rate of around 10%, which means about 27% of patients with normal colons will have a false-positive result over 10 years and need a colonoscopy.
One issue surrounding Cologuard tests - and it's a big one for many - is how insurance companies handle positive results. Insurers are required by law to fully cover screening colonoscopies. If a Cologuard test comes back positive, some carriers consider the follow-up colonoscopy to be "diagnostic" instead of "screening;" this may cause deductibles and other costs to come into play. News stories about patients who were caught off guard by having to pay for a colonoscopy after a positive Cologuard are prevalent.
Whether or not Cologuard is right for someone depends upon their risk tolerance, aversion to colonoscopy, and willingness to accept possible future costs. One other point about colonoscopies - in practice, gastroenterologists often recommend some type of shortened follow-up if they remove a polyp. Frequently, these polyps are very small, and current guidelines don't support early surveillance. Patients should be proactive about getting their pathology results so they can make sure any type of early follow-up is warranted. See polyp follow-up recommendations for more.