At-home stool tests offer a convenient way to screen for colorectal cancer, but most people fail to keep up with the yearly testing schedule, according to a large U.S. study.
When it comes to screening for colorectal cancer, colonoscopy was for many years considered the “gold standard.” That’s because colonoscopy is not only highly effective at detecting tumors in the colon and rectum, but it also helps prevent cancer by allowing doctors to remove any precancerous polyps they spot during the procedure.
In recent years, though, expert groups have recognized a stool-based test, called FIT, as an additional “top-tier” screening method for people at average risk of colorectal cancer. FIT—which stands for fecal immunochemical test—works by finding tiny amounts of blood shed from the lower intestines into the stool, which can be an indication of cancer.
While FIT does not match colonoscopy in detecting polyps, it is very good at catching cancer: Studies have shown that FIT screening may substantially lower the risk of dying from the disease (and it has largely replaced an older stool-based screening method called the fecal occult blood test, or FOBT).
And more and more, people are opting for stool tests over colonoscopy—a trend that accelerated during the Covid pandemic shutdowns. There are, however, some big caveats: If your stool test comes back positive, you need a follow-up colonoscopy to get a definitive diagnosis. And if your stool test is negative (no hidden blood detected), then you’re good for just one year. That is, to be most effective, it’s crucial that stool-based screening be repeated within the recommended time frame.
Based on the recent study findings, that is not happening for most people.
Behind schedule
For the study, published in the journal BMJ Public Health, researchers analyzed medical records from over 400,000 primary care patients in a large health system that spans seven U.S. states. They found that among patients who underwent stool-based screening for colorectal cancer and received a negative result, fewer than half had a repeat screening one year later.
The percentage of patients with repeat screenings varied somewhat during the study period, which covered 2018 through early 2022. But the rate consistently remained below 50 percent, and it hit its lowest point, at only 38 percent, shortly before the pandemic.
Meanwhile, among patients who did get a repeat screening after a negative stool test, many received it later than they should have—two to five months past the one-year mark. For a screening test that is supposed to be done annually, the researchers note, those extra few months are “meaningful”—potentially delaying cancer diagnosis and treatment.
Exactly why so few patients had timely repeat screenings is unclear—but it may be that the frequency of stool testing is simply too much for many people. Since the trend was apparent in the two years prior to Covid’s arrival in the U.S., it seems that pandemic-related disruptions to routine healthcare do not bear the blame.
FIT pros and cons
Over the past several decades, both screening and advances in treatment have improved colorectal cancer survival among Americans ages 55 and older. Still, the disease remains the second-leading cause of cancer deaths in the U.S. (after lung cancer), and screening rates are below target: About one-third of adults ages 45 and older are not up to date with any type of colorectal cancer screening.
Stool-based testing is one potential way to change that situation, especially for people who have difficulty accessing colonoscopy screening—due to lack of insurance, inability to travel to a colonoscopy facility, or other barriers. It may also encourage more screening among people who simply do not relish the idea of having a colonoscopy.
Stool tests can be done at home using a collection kit that you mail to a lab. And while that collection process may be less than pleasant, stool tests bypass the bowel preparation required for a colonoscopy—which, for many people, is worse than the procedure itself.
However, as the BMJ study illustrates, the frequency of stool-based screening can be a hurdle, too.
The takeaway: If FIT is your preferred colorectal cancer screening option, a single test is inadequate—regular follow-up testing is necessary for this approach to be meaningful, says Steven Jacobsohn, MD, a clinical professor emeritus of gastroenterology at UC San Francisco and a member of our editorial board. If you aren’t up to date, now is the time to get back on track, whether you are just a few months late or even more.
Bear in mind that people at average risk of the disease have multiple options for screening: Besides colonoscopy and FIT, there are stool DNA tests that only need to be done every three years—and, as of 2024, a blood-based screening test. Each method has its own benefits and limitations, and it’s important to talk with your doctor about the option that is best for you.
Another discussion point is when to stop screening. Routine colorectal cancer screening is recommended between the ages of 45 and 75 for people at average risk. For those ages 76 to 85, the decision should be individualized—based on their screening history, overall health, and personal preferences. Screening is not recommended after the age of 85.
Finally, it’s important to underscore that all of the above applies only to people at average risk of colorectal cancer. If you are at increased risk—due to factors such as a strong family history of the disease or a personal history of certain types of polyps—you should follow the screening type and frequency that your doctor recommends.
