Impact of introducing nucleic acid amplification testing for diagnosing Clostridioides difficile infection at a...

The pathogenicity of Clostridioides difficile infection (CDI) is caused by C. difficile toxins; therefore, accurate assessment of toxin production is clinically important. Although confirmatory testing for CDI is commonly used when stool samples show glutamate dehydrogenase-positive but toxin-negative results, the clinical impact of the shift from toxigenic culture (TC) to nucleic acid amplification testing (NAAT) remains unclear.

We retrospectively compared episodes confirmed using TC with those confirmed using NAAT between June 2021 and May 2025. The primary outcomes were CDI treatment rate and time to treatment initiation. The secondary outcomes were rates of isolation, contact precautions, and healthcare costs. A total of 209 episodes were analyzed. Among episodes with negative confirmatory test results, the NAAT group showed significantly lower rates of CDI treatment (TC vs. NAAT: 60.7% vs. 15.0%, p < 0.001), isolation (69.6% vs. 36.4%, p = 0.038), and implementation of contact precautions (88.9% vs. 50.0%, p < 0.001). Multivariate analysis showed that the introduction of NAAT was independently associated with reduced CDI treatment rates. Among episodes with positive confirmatory test results, treatment was initiated earlier in the NAAT group (median, 1 day vs. 0 days; p < 0.001). The healthcare costs were lower in the NAAT group.

Changing the confirmatory test from TC to NAAT reduced unnecessary CDI treatment and infection control measures during episodes with negative confirmatory test results. Furthermore, among episodes with positive confirmatory test results, rapid reporting by the NAAT enabled earlier treatment initiation. Confirmatory test selection could affect the diagnosis of CDI.