Study: Many People Don't Follow Up With a Colonoscopy After a Positive Stool Test

Only about half of patients follow up with a recommended colonoscopy after a positive at-home screening test for colon cancer, new research shows.

Though colonoscopies are the most common choice for colorectal cancer screenings in the U.S., many patients opt for less-invasive options, including at-home stool-based tests. But a positive result on a stool-based test—meaning the test discovered an abnormality—requires a follow-up colonoscopy to confirm a cancer diagnosis.

“A stool test can only predict the possibility of precancerous or cancerous lesions,” Dupinder Singh, MD, a gastroenterologist and hepatologist at City of Hope cancer research and treatment center in Duarte, California, who was not involved with the new research, told Health. “But a colonoscopy helps us visualize the lesion, remove it, or take biopsies.”

With the increased widespread use of these at-home tests—particularly during the COVID-19 pandemic—researchers sought to better understand the follow-up colonoscopy rates among patients with a positive stool-based test.

Low Follow-Up Rates Among Average-Risk People

For the new study, published last week in the JAMA Network Open, researchers analyzed anonymized administrative claims and electronic health record data of nearly 33,000 patients—all of whom were 50–75 years old, and had received a positive stool-based test result between June 2017 and June 2020.

The study population was nearly evenly split between male and female participants; the majority were white (88%), while 6.4% were Black, and 2.5% were Hispanic. Every person was considered at average risk of colorectal cancer.

After an initial positive test result, patients were followed for up to one year to track when—or if—they received a follow-up colonoscopy. Just 56% of people followed up with a colonoscopy within a year of a positive stool-based test; 51% followed up within six months.

The researchers found that a person’s socioeconomic status, the type of insurance they carried, as well as the COVID-19 pandemic all appeared to be factors that influenced whether or not a person followed-up. 

As part of the study, researchers also conducted interviews with physicians—all of whom said they were unaware of how low follow-up colonoscopy rates were among those who received a positive stool-based test.

“Most physicians we interviewed were shocked about how few people were following up,” study co-author Elizabeth Ciemins, PhD, MPH, MA, vice president of research and analytics at the American Medical Group Association, told Health, noting that most physicians believed the follow-up rate to be around 100%.

Positive Stool-Based Tests Require Follow-Up Colonoscopies

The American Cancer Society and the U.S. Preventive Services Task Force both recommend regular screening for colorectal cancer begins at age 45 for adults at average risk of the disease. This can be done through a visual exam of colon, like a colonoscopy, or a stool-based test.

There are several types of stool-based tests that can be used to screen for colon cancer: a fecal immunochemical test (FIT), a guaiac-based fecal occult blood test (gFOBT), or a multi-targeted stool DNA test (mt-sDNA).

Each stool-based test requires a stool sample that gets sent to a lab where it’s then screened for hidden blood in the stool, and/or abnormal DNA shed from cancer or polyp cells.

Because colonoscopies can be invasive and unpleasant, many people opt for the ease of taking a screening test at home.

“Patient adherence for screening is much higher with stool-based tests,” Ciemins said, adding that some research shows only about 38% of patients will willingly undergo a colonoscopy, compared to about 57% who are offered a stool-based test.

However, if a stool-based test yields a positive (abnormal) result, a follow-up colonoscopy is recommended, ideally within six to nine months, or earlier.

“Not following up on a stool based test is the equivalent of not following up on a positive mammogram,” Ciemins said.

Research published last year in the journal Gut found that people who had a positive FIT result, but who didn’t follow up with a recommended colonoscopy, were twice as likely to die compared to people who did undergo a follow-up colonoscopy.

The study, conducted by researchers in Italy, also followed more than 111,000 people who received a positive FIT result—more than 88,000 followed up with a colonoscopy within a year, while more than 23,000 did not get a follow-up colonoscopy.

Though cancer death rates in each group were small—under 1%—those who didn’t get a follow-up colonoscopy were about twice as likely to die of colorectal cancer over the next 10 years, compared to those who did.

Hurdles Keeping People From Accessing Further Testing

Screening for all cancers declined during the pandemic, CDC data shows. This is due to a combination of primary clinics closing, understaffing as resources were allocated to take care of COVID patients, and patients themselves avoiding healthcare settings out of fear of being exposed to the virus.

But there are also evergreen disparities that may be keeping people from being able to get into their doctors’ office, such as lack of insurance coverage, co-pays they can’t afford, or being unable to miss work.

On top of that, colonoscopies aren’t exactly viewed as a fun procedure. Dr. Singh, however, said most people do not experience any pain and do undergo some type of anesthesia, and that fear of the procedure itself should not prevent patients from getting a potentially life-saving colonoscopy.

Socioeconomic barriers may be more difficult to remove, and will require systemic changes in healthcare.

According to Ciemins, healthcare systems need to have their own ways of following up with patients. While a physician’s performance is measured partly on how many screenings are prescribed to patients that fall into the recommended window for colon cancer screening, they are not measured on whether or not these patients who have positive stool-based tests follow-up with a colonoscopy.

“This would be something that health systems could be measured on so they could become aware,” Ciemins said. “Then it could prompt individual tracking of patients where they reach out to patients who have not followed up.”

But overall, a low follow-up rate for colonoscopy screening should not be the norm, and more resources and education opportunities should be provided to those who undergo the tests.

“While we understand patients’ concerns, a colonoscopy is the gold standard to diagnose and detect colon cancer,” said Dr. Singh. “If a doctor recommends it, do it.”