Evaluation of BD GeneOhm CDiff PCR Assay for Diagnosis of Toxigenic Clostridium difficile Infection

Clostridium difficile is the most common infectious cause of nosocomial diarrhea, affecting thousands of patients annually and exacting enormous costs on the U.S. health care system. Early diagnosis is critical to prevent transmission and reduce morbidity and mortality, yet sensitive and specific diagnostic tests with a quick turnaround time are lacking. The objective of this study was to determine if a new commercially available real time polymerase chain reaction (PCR) test would prove more rapid, sensitive and specific than standard methods for the diagnosis of C. difficile infection (CDI). BD GeneOhmTM Cdiff assay, a real-time PCR assay for detection of C. difficile toxin B (tcdB) gene, was compared with Tox A/B IITM ELISA and a two-step algorithm which includes C. Diff Chek-60TM Glutamate Dehydrogenase (GDH)-antigen assay followed by cytotoxin neutralization. Four-hundred liquid or semisolid stools submitted for diagnostic C. difficile testing were selected: 200 GDH antigen-positive and 200 GDH antigennegative. All samples were tested by the C. Diff Chek-60TM GDH antigen, cytotoxin neutralization, Toxin A/B IITM ELISA, and BD GeneOhmTM Cdiff assay. Discrepant specimens were tested by toxigenic culture as an independent gold standard. Chart review was performed on patients with discrepant specimens. As BD GeneOhmTM Cdiff assay was not FDA-cleared at the time of study, PCR results were not clinically reported. Of 200 GDH-positive samples, 71 were positive by Tox A/B II, 88 were positive by the two-step method, 93 were positive by PCR, and 96 were positive by GDH-antigen only. Of 200 GDH-negative samples, 3 were positive by PCR only. Toxigenic culture was performed on 41 samples with discrepant results and 39 were culture-positive. After