Mayo spins rosy tale on Cologuard cancer screen — ignoring costs, false-positives and other crucial context


The Cologuard test kit

When we review news releases, we aim to put claims into broader context as well as observe whether the release describes the proposed intervention’s limitations and costs, among others elements, just as we do with news stories.

These key components were noticeably absent from a recent news release issued by the Mayo Clinic titled “Mayo Clinic: Cologuard Stool DNA Test Accurate in Screening for Colorectal Cancer in Alaska Native People.”

The benefits of a fecal DNA test kit that allows an individual to mail a stool sample from remote, under-served areas seems clear on the face of it. An accurate, non-invasive test could improve the effectiveness of colorectal cancer screening and help advocates for increased screening to reach their goal of 80% screened by 2018. But it’s important to put studies into broader context. In this case the study involved 661 native Alaskan volunteers who submitted stool samples for the Cologuard DNA test and the commonly used fecal immunochemical test (FIT). These individuals also underwent a colonoscopy, the gold standard in colon cancer screening and detection.

The release quotes David Ahlquist, MD, a study co-author and inventor of the stool DNA test:

“The high detection rates of cancer and large polyps by stool DNA that we found in the Alaska Native population are remarkably similar to those demonstrated in the multicenter 10,000 patient screening study of the general U.S. population reported in the New England Journal of Medicine in 2014.”

But the release doesn’t mention the test’s sensitivity in detecting advanced pre-cancerous lesions (42%) compared to FIT (24%), according to the previous and much larger research study published last fall in the NEJM.  It makes no mention of false positives (13%) that limit the test’s accuracy. That study of nearly 10,000 volunteers concluded that “In asymptomatic persons at average risk for colorectal cancer, multitarget stool DNA testing detected significantly more cancers than did FIT but had more false positive results.”

The news release also omits the manufacturer’s and the medical community-at-large’s directive that a positive test result requires patients to undergo a colonoscopy. Although that may be understood by medical experts, it shouldn’t be assumed that a lay reader of the news release understands this.

While short on that kind of information, the release is long on promotional-sounding quotes, including one from Robert Diasio, MD, who calls the results “impressive” and says the test “represents an accurate, patient-friendly and readily accessible new option that we hope will lead to improved screening participation rates in Alaska and across the country.”

Cologuard costs are the elephant in the room. James Allison, MD, clinical professor of medicine emeritus at UCSF’s division of gastroenterology, said his 2014 response to CMS regarding their approval of Cologuard is still relevant. His concerns about the cost of the tests and who pays are on-going. Allison asked:

“What is covered by the price the manufacturer is asking to receive (somewhere between $300-600)? Who pays for the shipping the specimen? What is the actual cost to the lab to run the test? Does CMS have any regulations on how price is determined by the manufacturer? With FIT available at $23 maximum, is the small increased application sensitivity of Cologuard compared to OC Sensor (the FIT comparator) in the NEJM study worth it? A formal cost effectiveness analysis should be done before recommending such reimbursement.”

CMS has since settled on a reimbursement rate of $502 per test, according to Allison. We should expect to see these costs addressed in news releases.

The timing of the release is noteworthy because there’s ongoing debate about the appropriateness and cost-effectiveness of the test. While both the FDA and CMS (which recommended approving Medicare coverage of the test for enrollees) had approved the Cologuard test last year, the US Preventive Services Task Force (USPTF) recently concluded in its draft colon cancer screening guideline update that Cologuard should be used as an “alternative screening” tool in certain populations, rather than a “recommended” test.

As a result, shares of Exact Sciences, the Mayo’s commercial partner for the testing venture, “plunged more than 45%,”according to The Motley Fool, a company that advises stock investors. “Put simply, the market is deeply concerned that this initial recommendation will lead to push back from private payers, hurting the company’s bottom and top-lines.” has previously written about other news reports on the Cologuard test that also lacked key details.

Often, but not always, problems with a news story originate with a news release. We hope reporters covering the latest Cologuard study give it the even hand that it deserves.

Update: contributor Richard Hoffman, MD, professor of internal medicine and epidemiology and director of internal medicine for the University of Iowa Carver College of Medicine/Iowa City VA Medical Center, weighed in with additional observations about the release.

“There’s no evidence that the new test will reduce colorectal cancer mortality—never been studied.  The RCTs [randomized controlled trials] showing benefit for fecal blood testing and flex sig showed a significant but small reduction in mortality—“entirely preventable” is a bit hyperbolic.”

He added, “The advantage of the Cologuard would be to reduce false positives—but the news release doesn’t address this potential advantage nor mention how many tests were positive.  The NEJM study did show a decreased specificity for Cologuard compared to FIT.”


Kathlyn Stone is an associate editor for and a regular contributor to the blog. 

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Comments (2)

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November 4, 2015 at 8:09 pm

Not sure if we have evidence to state colonoscopy is the gold standard. Agree with the cost issue for cologaurd for patients. I wonder how many people actually want to mail in their entire bowel movement?

    Gary Schwitzer

    November 5, 2015 at 11:01 am


    Thanks for your note and for your reminder about unanswered questions about colonoscopy. Nonetheless, it is clear that colonoscopy is considered by many to be the standard of care, even if not what some would call a gold standard.

    If one did a simple search on our site using the search term “colonoscopy,” one would find many past articles raising questions about what is known and what isn’t.

    Gary Schwitzer