PEORIA — The advertising for Cologuard sounds great — a non-invasive test for colon cancer you can do in your home — no icky prep, no embarrassing test, no time off work.

But a national group of gastroenterologists concerned that the ads aren’t relating the whole story has begun a campaign to better educate people about Cologuard, a screening test that looks at DNA and detects hidden blood in stools.

“The advertisement doesn’t talk about the limitation of the test,” said Dr. Eli Kuga of the Illinois Gastroenterology Institute in Peoria.

While Cologuard is better than no testing, it’s not the best option for most people, said Kuga. A 2014 study published in the New England Journal of Medicine found that 1 in 13 patients who use Cologuard may have cancer that the test will miss.

“That’s a significant number considering more than 1 million people have used this test,” said Kuga.

The study also found that Cologuard missed more than 30 percent of polyps that will become cancer, and almost 60 percent of polyps that could potentially become cancer.

“Those findings are significant. It shows this test is not as good as colonoscopy,” said Kuga.

Colonoscopy is the gold standard for detecting cancer of the colon, a completely preventable disease, said Kuga.

“Colon cancer starts as a polyp, a small growth in the lining of the colon. It grows for 10 years before it becomes cancer, so we have the opportunity to go in and remove it before it becomes cancer,” he said.

Not only does colonoscopy help doctors detect cancer, it also allows them to stop cancer before it begins through the removal of polyps. If a patient has a positive Cologuard test, they will still have to undergo a diagnostic colonoscopy to assess the situation and remove polyps.

An additional issue with Cologuard is that it results in a fairly high number of false positives — 13 percent. Not only does this cause unnecessary worry for the patient, undergoing a second test is expensive. While health insurance pays 100 percent of a screening colonoscopy, a diagnostic colonoscopy generally requires out-of-pocket expense for the patient, said Kuga.

Another thing that makes colonoscopy a better choice is that it only needs to be done every 10 years — Cologuard should be done every three years, said Kuga.

But even as Kuga points out the limitations of Cologuard, he is quick to add that it’s much better than no screening at all.

“Any test is better than no testing,” he said. “The best test is colonoscopy, but if patients don’t want it — they’ve heard horror stories about it — then I recommend fecal occult blood testing to check for hidden blood in the stool, based on the fact that early cancer bleeds very slowly.”

His third choice is Cologuard, primarily because it has more false positives than fecal occult blood testing.

The Centers for Disease Control and Prevention recommends that everyone age 50 to 75 should get a colonoscopy every 10 years. People with high risk factors, like a family history of colon cancer or inflammatory bowel disease, will need to be tested more frequently and starting at a younger age.

“Right now the screening rate is low in Illinois, 63 percent. The national average is about 67 to 68 percent,” Kuga said. “We need to raise the screening rate in Peoria.”

Leslie Renken can be reached at 686-3250 or lrenken@pjstar.com. Follow her on Twitter.com/LeslieRenken, and subscribe to her on Facebook.com/leslie.renken.