As previously noted, CDI is traditionally diagnosed by a variety of methods, including a review of past medical history, an examination of signs and symptoms, and laboratory-based testing. In the past, laboratory reference methods included the selective anaerobic culture to detect the growth of Clostridiodes difficile and the cell culture cytotoxicity assay to detect toxin-producing strains of C. difficile. In fact, many considered the cell culture cytotoxicity assay as the gold standard test to diagnose CDI.
However, these two tests do have limitations such as long turnaround times, and technical complexities, often leading to a delay in proper treatment. Because of these limitations, facilities and clinicians more frequently use EIA testing (for toxins A, B, GDH antigen) and NAAT assays to more rapidly identify CDI. There are many commercially available EIA tests for CDI that provide a rapid test result with good specificity at a low-test cost.
