Multitarget stool DNA (MT-sDNA) testing is used in primary care as a screening test for colon cancer. Test effectiveness and patient compliance were examined in clinical practice.

We assessed outcomes of MT-sDNA testing in a cohort study conducted in a large integrated healthcare system comprising 15 hospitals and 150 outpatient clinics using advanced electronic data capture (Clarity2 [Epic, Verona, Wisc, USA] and REDCap [Encinitas, Calif, USA]) followed by manual chart review to confirm MT-sDNA test results and to monitor the outcomes of subsequent colonoscopy.

A total of 6835 MT-sDNA tests were performed over 1 year between 2017 and 2018. Of 1242 patients (18%) who tested positive, 1109 (89%) were referred for colonoscopy, and 905 of them (73%) underwent colonoscopy. Eleven patients (<1%) with a positive test had colorectal cancer, 215 (17%) had advanced adenomas, 110 (9%) had serrated adenomas, and 546 (60%) patients had an adenoma. Of the 6835 patients tested, adenoma or cancer was found in 557 patients (8%). An advanced adenoma or cancer was found in 226 of 1242 patients with a positive test (18%). Nonadherence with colonoscopy after a positive test was high (21%), and the cost to detect 1 advanced adenoma or cancer was $38,849.

The frequency of adenoma detection by an MT-sDNA screening strategy is low, and many positive tests are not associated with significant findings at colonoscopy. Failure to follow a positive test with colonoscopy is a significant problem that needs to be considered when this screening strategy is adopted.