1 in 10 Stool-Based CRC Tests Can’t Be Processed

Roughly 10% of fecal immunochemical tests (FIT) used for colorectal cancer (CRC) screening by a safety-net health system contained unsatisfactory samples that could not be processed.

And fewer than half of patients with unacceptable FIT samples completed a follow-up test within 15 months, a large retrospective study finds.

“The high prevalence of unsatisfactory FIT in our study, which in most instances was not followed by a timely subsequent test, highlights the need for systems to have a better, more comprehensive approach to flagging and following up unsatisfactory FIT,” study investigator Rasmi Nair, MBBS, PhD, with UT Southwestern Medical Center, Dallas, Texas, told Medscape Medical News.

Unsatisfactory tests are worrisome because the patient may remain unscreened, Aasma Shaukat, MD, MPH, director of outcomes research, Division of Gastroenterology and Hepatology, NYU Langone Health, who wasn’t involved in the study, told Medscape Medical News.

When a mailed test fails, the best approach is to send another test and tell the patient what steps were missed, but often that doesn’t happen, she said.

“The provider may wonder what happened and months may go by before anybody picks up on the problem, or the patient is just unwilling to do another test,” said Shaukat, professor of medicine and population health at NYU Grossman School of Medicine. “There needs to be some mechanism that gets triggered to reach out to the patient and ask about the test.”

The study was published online on November 15, 2023 in Cancer Epidemiology, Biomarkers & Prevention.

Cost-Effective When Done Right

The US Preventive Services Task Force (USPSTF) recommends FIT as an option for annual CRC screening in adults aged 45-75 years. For many, including uninsured and lower-income individuals, FIT may be less expensive and more accessible than getting a colonoscopy.

But the effectiveness of FIT depends on the patient returning a satisfactory sample and clinician follow-up when the test is abnormal.

Using EHRs, Nair and colleagues identified 56,980 individuals aged 50-74 years who underwent initial FIT screening from 2010 to 2019 as patients of Dallas-based Parkland Health, a safety-net health system that primarily serves an uninsured, lower-income, and racial/ethnic minority population.

Altogether, 5819 of the tests (10.2%) were deemed unsatisfactory by the processing lab.

Reasons for unsatisfactory FIT were inadequate specimen (51%), incomplete labeling (27%), old specimen (13%), broken container or leakage (8%), and other (1%).

Relative to patients with a satisfactory index FIT, patients with a failed test were more likely to be male (odds ratio [OR], 1.1), be Black (OR, 1.46), primarily speak Spanish (OR, 1.12), have Medicaid coverage (OR, 1.42), or have a diagnosed comorbidity (OR, 1.14).

Mailed tests were more likely to produce unsatisfactory results (OR, 2.66) than were tests performed in a clinic. This finding could be because patients who obtained FIT by mail only received written instructions, whereas patients who received the test in the clinic likely were given more detailed or in-person instructions, the authors write.

Only 40.7% of individuals who returned an unsatisfactory FIT received follow-up FIT, colonoscopy, or other screening within 15 months of the failed test.

However, patients with unsatisfactory mailed tests were more likely to undergo repeat screening within 15 months (OR, 1.92) because the mail-order program included outreach for those with inadequate tests. Patients aged 50-54 years with a failed FIT also were more likely to complete a subsequent test (OR, 1.16).

A Problem Worth Fixing

These results point to the need to design “comprehensive patient education and system improvement strategies to improve screening delivery in real-world settings,” Nair told Medscape Medical News.

Shaukat noted that the problem of FIT “failures” is not limited to safety-net health systems.

“The error rate is somewhere between 5% and 12% across different healthcare systems,” she told Medscape Medical News.

One of the biggest failings is that the test requires the patient to write the date of collection, Shaukat said. That’s a “cumbersome step that a lot of patients just forget to do or are unable to do. Without a date on it, a lot of labs choose not to process it,” she explained.

Another issue is that many labs require a 48-hour window for sample return.

“A patient may collect the sample but forget to toss it in the mail the next day and there’s a weekend or holiday and it may take longer than the 48-hour window for the lab to receive it,” Shaukat said.

Tackling the problem of FIT failures is a problem worth fixing because a FIT-first approach is easier and more cost-effective than colonoscopy is for screening, Shaukat said.

“If there are 100 eligible patients to be screened for CRC, that would be 100 colonoscopies upfront,” she said. “However, if 100 patients could be mailed FIT and they were to return it with satisfactory samples, using the positivity rate of about 5%-7%, there will be seven patients that then need to be triaged to colonoscopy and the others can wait a year to get screened.

“The FIT cost is about $20, which is a lot more economical than colonoscopy,” Shaukat said.

Funding for this study was provided by the National Institutes of Health and the Cancer Prevention and Research Institute of Texas. Nair and Shaukat have no relevant conflicts of interest.