Evaluation of Glutamate Dehydrogenase Immunoassay Screening with Toxin Confirmation for the Diagnosis of Clostridium difficile Infection

Clostridium difficile infections (CDIs) cause significant morbidity and increased hospital stays. Rapid and sensitive detection algorithms are needed to properly manage patients with suspected CDI. To determine the best algorithm for detection of CDI, we evaluated 2 assays for glutamate dehydrogenase (GDH) bacterial detection and toxin confirmation by enzyme immunoassay (EIA), cell culture neutralization (CCNA), and toxin B gene polymerase chain reaction (PCR). The 2 GDH screening methods had 76% and 90% sensitivity, respectively, for PCR-positive stool samples. Sensitivity and specificity compared with CCNA were 66% and 99% for toxin B EIA and 98% and 75% for PCR. Discrepancy analysis using toxigenic culture indicated a revised specificity for PCR of 93%. Review of the medical records of 8 patients with GDH-negative, PCR-positive stools showed that 1 patient had a false-negative result in 1 of 2 GDH assays, and data from 7 patients were believed not to represent true CDI cases. Use of a sensitive GDH-screening assay followed by PCR toxin confirmation is an efficient algorithm for detection of CDI.