Some literature in recent years has suggested that assays for GDH, an enzyme produced by C. difficile, could provide a more sensitive means of screening for C. difficile.
Published studies have indicated that toxin immunoassays by themselves may not provide adequate sensitivity for detection. Several investigators have examined the utilization of a two-step algorithm.
A negative result for GDH has been associated with a high value for the prediction of a true negative result; however, the results of antigen testing alone are nonspecific. A positive result is not necessarily associated with a toxin-producing strain. Therefore, a second assay should be used to augment the antigen test. Antigen assays have been employed in combination with tests for toxin detection, molecular PCR, or toxigenic culture in two-step testing algorithms as displayed in the diagram.6,7
6. McDonald, L, Gerding, D, et al. "Clinical Practice Guidelines for Clostridium difficile Infection in Adults and Children: 2017 Update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA)." Clinical Infectious Diseases, vol 66, issue 7, 1 Apr 2018, pages e1–e48, https://doi.org/10.1093/cid/cix1085.7. C. diff (Clostridioides difficile). Centers for Disease Control and Prevention (CDC). Revised 5 Oct 2022. https://www.cdc.gov/cdiff/clinicians/faq.html.
