Application of diagnostic algorithms for Clostridioides difficile infection using a GDH/ toxin test for five years from a single center in Korea: a diagnostic accuracy study

Abstract

Background: Accurate diagnosis of Clostridioides difficile infection (CDI) requires bothmicrobiologic confirmation and clinical correlation. Current guidelines recommend a two-stepalgorithm combining a sensitive screening test with a specific confirmatory assay. This studyevaluated the diagnostic performance of the glutamate dehydrogenase (GDH)/toxin enzymeimmunoassay (EIA) over five years and assessed its suitability as an initial screening test. Methods: We retrospectively analyzed 8,685 C. difficile-related tests conducted betweenMarch 2020 to February 2025. The GDH/toxin EIA was performed using the C. DIFF QUIK CHEKCOMPLETE (TechLab). Toxigenic culture involved alcohol-shocked stool samples plated onchromogenic agar and incubated anaerobically for 48 hours. Toxin gene polymerase chainreaction (PCR) was done using the BD MAX Cdiff assay and the Xpert C. difficile assay. Results: The GDH test showed a sensitivity of 77.0% and negative predictive value (NPV) of95.1% compared with culture. The toxin EIA showed 35.0% sensitivity and 96.9% positivepredictive value relative to PCR. The combined GDH+Toxin EIA achieved 82.6% sensitivityand 96.9% NPV compared with PCR. Most discordant results involved low bacterial burden ornon-toxigenic isolates. GDH positivity correlated with growth quantity, and toxin EIA positivityvaried by ribotype. Algorithm modeling suggested the GDH/toxin test as a cost-effective firstline option. Conclusion: The GDH/toxin EIA demonstrated high NPV and may be appropriate as an initialtest in CDI diagnostic algorithms. These findings support its role in diagnostic stewardshipand provide evidence to inform the development of national diagnostic guidelines in Korea.