Cologuard has drawbacks, but better than doing nothing

My column on a home colon cancer test had readers pointing out drawbacks: false positives and insurance problems.

SHARE Cologuard has drawbacks, but better than doing nothing
A technician labels tubes at Exact Sciences Laboratories. With two dozen steps to the testing procedure over a period of days, making sure patient information stays with every sample is a priority.

A technician labels tubes at Exact Sciences Laboratories. With two dozen steps to the testing procedure over a period of days, making sure patient information stays with every sample is a priority.


Three times a week is a lot to stand on my little newsprint soapbox, raise a tin trumpet to my lips, and blow.

So if I expect you to regularly listen, I’d better not sound the same note, but skip from one tune to another. Because repetition is boring. But sometimes a shoe is left dangling, such as when I wrote about the Cologuard colon cancer test on Sept. 8

Reaction fell into two camps. Those grateful to learn of this new way to detect colon cancer with a home test. And those concerned with aspects I didn’t address.

Opinion bug


“Your comprehensive article on Cologuard does not cover the most obvious question — how many false positives? False negatives?” wrote Dr. Robert W. Brandstatter, a North Side dentist.

“We have no real data to help guide patients and clinicians with what to do after a Cologuard test is done,” wrote Dr. Tibor Krisko, a New York gastroenterologist and assistant professor at Weill Cornell Medical in New York City. “If positive, a colonoscopy is clearly warranted (though there is evidence to suggest many people with positive results do not get the all-important, potentially life-saving colonoscopy).”

The traditional colonoscopy — a doctor snakes a tiny camera into your intestines to look for tumors — has drawbacks. You must go to a hospital or clinic, risky in the age of COVID. You’re under anesthesia or sedation, also presenting risks. Doctors might perforate your colon with the probe. The procedure is uncomfortable, time-consuming and expensive. So 40% of adults skip the test, despite its big benefit: detecting cancer when early and treatable instead of advanced and lethal.

Cologuard has an 8% false negative rate — you have cancer, but the test misses it. Colonoscopies have a 5% false negative — the doctor isn’t thorough when eyeballing your insides. Close enough for baseball. But Cologuard also misses about half of pre-cancerous polyps.

There are other issues. Cologuard has a 13% false positive rate — it suggests you have cancer when you don’t. This causes anxiety and requires the colonoscopy you were trying to avoid in the first place, which can cause problems with insurance.

“What nobody ever told me and I did not see it discussed in your column is that once you have a positive Cologuard result, the ensuing colonoscopy is no longer covered by insurance,” wrote a reader. “I ended up paying in excess of $5,000 for a procedure most insured people who do not take the Cologuard test have done and covered by insurance.”

What to do?

“The best test is the one the patient will get,” said Krisko. “Getting people into the colonoscopy suite is not without challenges. Cologuard has definite benefits, some downsides.”

Mary Fischer had a colonoscopy in 2005 to bring attention to the importance of the procedure.

Mary Fischer is one of three nurses who had a colonoscopy in 2005 in an effort to bring attention to the importance of the procedure.

Sun-Times file

“I’m a big advocate for high-quality colonoscopy,” said Rajesh Keswani, gastroenterologist at the Digestive Health Center at Northwestern Memorial Hospital. “We do know: one high quality colonoscopy, and you’re protected for 15 years. If I had a patient considering either a colonoscopy or a stool-based test, I’d absolutely tell them: the colonoscopy. It’s more likely to detect precancerous polyps.”

But there are other factors. With its low cost, home use, and ease, Cologuard appeals to those who won’t subject themselves to the colonoscopy. Keswani agrees it’s “way better than nothing,” bringing up an advantage of Cologuard I hadn’t considered: consistency.

“If you get a Cologuard, no matter what day you use it, it’s going to be the same sensitivity. ... If you order it on a Monday, a Wednesday or Friday, it doesn’t matter. It’s a standard test. If you order a colonoscopy, how effective it is is extremely related to who does the procedure.”

Some doctors look harder than others. Some spend three minutes snooping around your colon. Others spend up to 14. The harder they look, the more they find. 

“There is up to a four-fold difference ,” Keswani said. “There is a four times reduced likelihood of developing cancer based on who does your colonoscopy. The problem is, how do you figure that out?”

See? That’s the trouble with my job. No matter how much a thread is pulled, there’s always more left on the spool: for instance, my test was negative, so I’m fine, probably. How to pick a good gastroenterologist seems an excellent topic for a column. But then I’ll risk morphing into the medical reporter, and not the spinning carnival wheel of wonder you’ve come to expect.

Tell you what: in three years, when its time for me to test again, I’ll go the colonoscopy route, first determining how to locate a gastroenterologist who is more long-look instead of quick-glance. We’ll pick up this subject in 2023. I plan to be here, and hope you will be too. In the meantime, getting your colon checked, in some fashion, will help ensure you’re around to read it.

The Latest
Daryl Hall, in a court filing, accuses musical partner John Oates of moving to sell his share of the team’s joint venture. A court hearing is scheduled for Thursday.
Authorities suspect the woman was the victim of a homicide. Her body was found early Wednesday by the side of a road in Old Mill Creek.
A 22-year-old man was in a parking lot in the 8700 block of South Lafayette Avenue when he was struck by gunfire about 5:10 p.m. Wednesday police said.
A male, age unknown, was in the 7700 block of South Bishop Street about 7 p.m. Wednesday when he was shot multiple times in the body, police said.