At-home tests for colon cancer make this important screening readily available to folks who can't afford or would rather not go through a colonoscopy.

Unfortunately, more than 1 in 10 at-home tests sent to a lab are unusable, mainly due to mistakes made by the patient, a new study reports.

"The study underscores the importance of addressing breakdowns in the screening process, particularly in specimen collection and labeling," researcher Rasmi Nair, an assistant professor of public health at UT Southwestern in Dallas, said in a news release.

The U.S. Preventive Services Task Force recommends that people who are between 45 and 75 be regularly screened for colon cancer.

One option is a fecal immunochemical test (FIT), which uses antibodies to detect blood in the stool that's not visible to the eye.

These tests are done once a year, and are cheaper and easier than procedures like colonoscopy, researchers said.

For the test, a person takes a sample of their stool, labels it, and then sends it to a lab for analysis.

Nair and her colleagues suspected that many of these tests couldn't be processed properly due to patient mistakes, so they looked at in-home fecal immunochemical tests sent in by nearly 57,000 people between 2010 and 2019.

The tests were all submitted by people being treated at Parkland Health, a safety net hospital in Dallas County that serves as UT Southwestern's primary teaching hospital.

Researchers found that more than 10% of FIT samples couldn't be processed by the lab.

In about half of those cases (51%), the patient hadn't taken an adequate stool specimen.

Other problems included incomplete labeling (27%), a specimen that was too old (13%), or leaking or broken specimen containers (8%), researchers said.

Failure rates were higher among patients who were male, Black, Spanish-speaking or on Medicaid, results show.

In addition, patients who received their kit in the mail rather than from a health care professional were at greater risk of making a mistake that would render the sample unusable, researchers found.

These results show the need for better patient education on taking and sending a sample, as well as improved test-tracking procedures and timely follow-up when a sample isn't usable, researchers said.

These findings should apply to other sorts of at-home tests as well, Nair added.

"Our findings could impact other at-home tests such as fecal DNA tests for CRC [colorectal cancer] screening and future home testing for human papillomavirus, for instance," she said. "Understanding the reasons for unsatisfactory home tests, implementing automatic ordering of subsequent tests, and ensuring appropriate completion of tests and follow-up become increasingly important."

The findings were recently published in the journal Cancer Epidemiology, Biomarkers & Prevention.

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