Comparison of Real-Time PCR Techniques to Cytotoxigenic Culture Methods for Diagnosing Clostridium difficileInfection

ABSTRACTIn the past decade, the incidence of Clostridium difficileinfections (CDI) with a more severe course has increased in Europe and North America. Assays that are capable of rapidly diagnosing CDI are essential. Two real-time PCRs (LUMC and LvI) targeting C. difficiletoxin genes (tcdB, and tcdAand tcdB, respectively) were compared with the BD GeneOhm PCR (targeting the tcdBgene), using cytotoxigenic culture as a gold standard. In addition, a real-time PCR targeting the tcdCframeshift mutation at position 117 (?117 PCR) was evaluated for detecting toxigenic C. difficileand the presence of PCR ribotype 027 in stool samples. In total, 526 diarrheal samples were prospectively collected and included in the study. Compared with those for cytotoxigenic culture, sensitivity, specificity, positive predicted value (PPV), and negative predicted value (NPV) were for PCR LUMC 96.0%, 88.0%, 66.0%, and 98.9%, for PCR LvI 100.0%, 89.4%, 69.7%, and 100.0%, for PCR ?117 98.0%, 90.7%, 71.9%, and 99.5%, and for PCR BD GeneOhm 88.3%, 96.9%, 86.5%, and 97.4%. Compared to those with feces samples cultured positive for C. difficiletype 027, the sensitivity, specificity, PPV, and NPV of the ?117 PCR were 95.2%, 96.2%, 87.0%, and 98.7%. We conclude that all real-time PCRs can be applied as a first screening test in an algorithm for diagnosing CDI. However, the low PPVs hinder the use of the assays as stand-alone tests. Furthermore, the ?117 PCR may provide valuable information for minimizing the spread of the epidemic C. difficilePCR ribotype 027.