PHILADELPHIA — Mailing in your stool may not be the best way to screen for colorectal cancer. Scientists from the Dallas-based Parkland Health system found that more than 10 percent of fecal immunochemical tests (FIT) used for routine colorectal cancer (CRC) screening produced unsatisfactory samples that could not be processed.
FIT is a self-collected test that detects hidden blood in the stool and is recommended by the U.S. Preventive Services Task Force for annual CRC screening among individuals 45 to 75 years-old. For many, especially those without insurance or from medically underserved groups, FIT is a cost-effective and accessible screening option compared to alternatives like colonoscopy or stool-based tests checking for tumorigenic DNA.
“FIT is the test of choice, particularly in large population-based settings where access to screening colonoscopy is limited,” says study co-first author Dr. Rasmi Nair, an assistant professor at the Peter O’Donnell Jr. School of Public Health of the University of Texas Southwestern Medical Center, in a media release. “Even when colonoscopy is available, many would prefer to do the simple, noninvasive stool test.”
While previous studies have focused on increasing FIT participation, this research delved into the frequency of unsuccessful screening due to issues with sample collection, labeling, or storage. It also examined the extent to which patients who submitted unsatisfactory samples received follow-up testing.
“The effectiveness of FIT depends on the satisfactory completion of multiple steps — participation, test completion, follow-up of abnormal results, and repeat testing annually,” explains study co-first author Dr. Po-Hong Liu, gastroenterology fellow at UT Southwestern Medical Center. “A break in the chain at any point can reduce the effectiveness of CRC screening.”
The study analyzed data from 56,980 individuals between 50 and 74 who underwent FIT screening between 2010 and 2019 within the Parkland Health system. The results revealed that 10.2 percent of the tests were unsatisfactory. The reasons for this included inadequate specimens (51%), incomplete labeling (27%), samples being too old (13%), or broken or leaking containers (8%). Most concerning is that only 40.7 percent of individuals with unsatisfactory tests received follow-up FIT or colonoscopy screening within 15 months of the failed test.
“The fact that, in most instances, unsatisfactory FIT was not followed by a timely subsequent test highlights the need for systems to have a better, more comprehensive approach to tagging and following up unsatisfactory FIT,” notes Dr. Liu.
Mail-order tests were found to be 2.66 times more likely to produce unsatisfactory results than tests conducted in a clinic, likely due to the technical assistance available in clinical settings. However, patients with unsatisfactory mail-order tests were 1.92 times more likely to undergo repeat screening within 15 months, thanks to the automatic distribution of repeat tests.
The study also uncovered racial and ethnic disparities in satisfactory FIT completion, with Black patients being 1.46 times more likely to submit unsatisfactory tests, and patients primarily speaking Spanish being 1.12 times more likely to do so.
To improve the accuracy and completeness of sampling, study authors suggested potential solutions such as wordless or low-literacy instruction pamphlets, pre-affixed patient labels or barcodes to minimize labeling errors, and automated systems for identifying and contacting patients with unsatisfactory tests.
While the study has some limitations, including its focus on a specific health system, reliance on brief laboratory notes, and potential follow-up care outside the system, it highlights the importance of addressing challenges in CRC screening to ensure early detection and better outcomes for patients.
The study is published in the journal Cancer Epidemiology, Biomarkers & Prevention.
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