Is At-Home Stool Test a Viable Alternative to Colonoscopy?

MONDAY, Feb. 25, 2019 (HealthDay News) -- Simple at-home stool tests are a reliable way to screen for colon cancer -- and a good alternative to invasive colonoscopies, a new research review confirms.

The analysis, of 31 studies, looked at the effectiveness of the fecal immunochemical test, or FIT -- which detects hidden blood in the stool. It found that a one-time FIT screening caught up to 91 percent of colon cancers in people at average risk of the disease.

Experts said the findings offer more support for a screening test that has long been a recommended option -- but not often performed in the United States.

Instead, most Americans are screened for colon cancer by colonoscopy -- an invasive test that examines the colon. However, many other countries favor a yearly stool test.

"For the average-risk person, there are good alternatives to colonoscopy screening, and people should be aware of that," said Dr. Thomas Imperiale, the senior researcher on the review. "That's the bottom line."

Imperiale is a gastroenterologist with the Indiana University School of Medicine and Regenstrief Institute, in Indianapolis.

He said that in his experience, patients sometimes arrive for a colonoscopy screening having never heard about any other options from their primary care doctor.

"I think we need to be more forthright with patients about all their options," Imperiale said.

The findings were reported online Feb. 26 in Annals of Internal Medicine. They're based on more than 120,000 patients who had FIT screening and a subsequent colonoscopy.

For the FIT screening, a doctor supplies a test kit for patients to use at home. Different manufacturers make FITs. Depending on the specific test, the review found, a one-time screening caught around three-quarters to 91 percent of colon cancers.

That makes a one-time FIT less sensitive than a one-time colonoscopy. But, Imperiale pointed out, FIT screening is done yearly, while colonoscopy is done every 10 years.

Plus, he said, some people who are not willing to undergo a colonoscopy might be OK with a stool test. And it's getting screened that matters, Imperiale said.

An editorial published with the study points to some hard numbers: Only two-thirds of Americans aged 50 to 75 have been screened for colon cancer, mostly by colonoscopy. Of the one-third who remained unscreened, many are lower-income, uninsured or "underinsured."

Greater awareness of cheaper, easier FIT screening -- among doctors and patients alike -- could help close that gap, said Dr. James Allison, the editorial author.

For years, Allison said, the media and health systems have promoted colonoscopy screening as the "gold standard" -- while FIT is often regarded as "second-best."

But the evidence does not support that.

"There is no single best test for colon cancer screening," said Allison, who is with the University of California, San Francisco and the Kaiser Permanente Northern California Division of Research.

And, he pointed out, guidelines on colon cancer screening do not advocate any one test over the others.

Guidelines from the U.S. Preventive Services Task Force say that people at average risk of colon cancer should begin screening at age 50. The American Cancer Society suggests age 45. But both groups say screening can be done with stool tests, colonoscopy or sigmoidoscopy (another invasive test).

Colonoscopies are much better than FIT at detecting polyps -- benign growths that occasionally become cancerous. But, Imperiale said, research suggests that large, "advanced" polyps transition to cancer at a rate of 3 to 6 percent per year. So if one FIT misses a large polyp, there's a good chance it will still be caught during subsequent tests.

And while colonoscopies are generally safe, they do carry small risks of bleeding, infection or bowel tears.

"We need to recognize that FIT is at least as good as colonoscopy," Allison said.

There is another type of stool-based screening test available, called Cologuard. It looks for both hidden blood and certain DNA changes that can be found in colon cancers or polyps.

But the test is expensive -- around $500 -- and there's no proof it's better than FIT screening, Allison said.

People who choose stool testing will not necessarily avoid a colonoscopy. If blood is detected, you'll need a follow-up colonoscopy -- and it may turn out to be a false alarm. Keeping up the yearly schedule is also key, Imperiale said.

More information

The American Cancer Society has more on colon cancer screening.