A multicenter evaluation of a sample to answer real-time PCR assay for toxigenic C. difficile in symptomatic subjects

We evaluated the performance of the Luminex ARIES® C. difficile Assay on 984 stool specimens prospectively collected from patients being tested for CDI at 4 clinical laboratories in the United States. Results were compared to direct and enriched toxigenic culture. Positive percent agreement (PPA) of the ARIES® C. difficile Assay was 98.1% versus direct toxigenic culture, and sensitivity versus direct plus enriched toxigenic culture was 90.5%. Negative percent agreement (NPA) of the ARIES® C. difficile Assay against direct culture was 92.6%, and specificity versus direct plus enriched toxigenic culture was 95.8%. The ARIES® C. difficile Assay was also compared to the results of routine (molecular, antigen, and/or toxin) methods for C. difficile testing used at each institution. The PPA of the ARIES® C. difficile Assay ranged from 82.9% to 100%. NPA values against these commercial assays ranged from 94.5% to 100%.