The American College of Gastroenterology has hit out at updated colorectal cancer screening guidelines for including blood-based testing, claiming the recommendation, while nuanced, could lead to missed cancers in patients.

Developed by the American Cancer Society and published in its flagship journal CA: A Cancer Journal for Clinicians [link here], the guidelines now recommend blood-based tests be offered as a “not preferred” screening option for patients who refuse or have not completed a colonoscopy or stool-based test.

The hope is to increase participation among previously unscreened individuals as a way of boosting screening uptake and reducing the burden of CRC. The guideline development group stressed patients should be counselled on the test’s limitations and informed of the need for follow-up colonoscopy if positive.

But in a public statement last month, the American College of Gastroenterology expressed concern that both doctors and patients might “not fully understand” the nuance around the guidance, resulting in uptake of the lower-performing screening test being “substantially more wide-reaching” than intended.

It pointed out the FDA-approved Guardant Shield blood test might miss one in every three early-stage cancers and one in six total cancers, compared with gold-standard colonoscopy, which had an estimated detection rate of over 95%.

“Between preconceived notions about blood tests, overly simplistic headlines, and commercial advertising, the “not preferred” distinction will be buried in clinical language that patients should not be expected to parse in the first place,” the college said.

“We want to be certain that the unscreened individuals are given genuine opportunity to complete a “preferred” test first, before being offered a blood test. The substitution of a “preferred” test for a blood test poses serious risks to patients due to its low sensitivity for detecting precancerous polyps and early-stage cancers.”

The concerns echoed an accompanying editorial at the time of the guidelines’ publication [link here], which highlighted qualitative research suggesting some patients incorrectly believed blood tests were more accurate than stool‐based tests.

“Because blood tests are less likely to find advanced adenomas than other available tests, the use of these tests in place of more effective screening tests could result in net harm (i.e., increased deaths from colorectal cancer),” said the editorial authors, who included prominent US gastroenterologist Professor David Lieberman from Oregon Health and Science University.

“Ultimately, the goal must remain reducing colorectal cancer deaths through screening programs that prioritise accuracy, equity, and informed patient choice, ensuring that the convenience of newer tests complements rather than compromises the effectiveness of population‐level cancer prevention.”