JCM Accepts, published online ahead of print on 28 October 2009

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J. Clin. Microbiol. doi:10.1128/JCM.01630-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Comparison of BD GeneOhm Cdiff Real-time PCR Assay with a Two-Step Algorithm and a Toxin A/B ELISA for Diagnosis of Toxigenic Clostridium difficile Infection

Elizabeth J. Kvach, David Ferguson, Paul F. Riska, and Marie L. Landry^*

Department of Laboratory Medicine, Yale University School of Medicine, and Clinical Virology Laboratory, Yale-New Haven Hospital, New Haven, CT; and Department of Medicine, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY

^* To whom correspondence should be addressed. Email: marie.landry{at}yale.edu.

BD GeneOhm^TM Cdiff assay, a real-time PCR assay for the detection of Clostridium difficile toxin B (tcdB) gene, was compared with Tox A/B II^TM ELISA and a two-step algorithm which includes C. Diff Chek-60^TM 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 antigen-negative. All samples were tested by the C. Diff Chek-60^TM GDH antigen, cytotoxin neutralization, Toxin A/B II^TM ELISA, and BD GeneOhm^TM Cdiff assay. Discrepant specimens were tested by toxigenic culture as an independent gold standard. 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 culture resolution of discrepants, Tox A/B II detected 70 (66.7%), the two-step method detected 87 (82.9%), and PCR detected 96 (91.4%) of 105 true positives. The BD Gene-Ohm^TM Cdiff assay was more sensitive in detecting toxigenic C. difficile than Tox A/B II (p <0.0001); however, the difference between PCR and the two-step method was not significant (p=0.1237). Enhanced sensitivity and rapid turnaround time make the BD GeneOhm^TM Cdiff assay an important advance in the diagnosis of toxigenic C. difficile infection.