Comparison of Illumigene, Simplexa, and AmpliVue Clostridium difficile Molecular Assays for Diagnosis of C. difficile Infection

We compared the performance of the Simplexa Universal Direct (Focus Diagnostics) and AmpliVue (Quidel Corporation) assays to that of the Illumigene assay (Meridian Bioscience, Inc.) for the diagnosis of Clostridium difficile infection. Two hundred deidentified remnant diarrheal stool specimens were tested by the Simplexa, AmpliVue, and Illumigene methods. Specimens with discrepant results among the three assays and a representative number of concordant specimens were further evaluated by toxigenic culture. The sensitivity and specificity were 98 and 100% and 96 and 100% for the Simplexa Universal Direct and AmpliVue assays, respectively. Both assays are easy to perform, with rapid turn-around-times, supporting their utility in the clinical laboratory as routine diagnostic platforms.