Applicability of commercial multiplex kit for the diagnosis of: a multicenter investigation Clostridium difficile infections / 中华检验医学杂志

ABSTRACT

Objective To evaluate the performance of Xpert C. difficile multiplex real-time PCR assay for diagnosis of Clostridium difficile infections in Chinese hospital settings. Methods This study was performed in Huashan Hospital, Ruijin Hospital, Beijing Hospital, Nanfang Hospital and Sir Run Run Shaw Hospital using a standard study protocol. Unique unformed stools from patients with acute hospital-acquired diarrhea were simultaneously analyzed by toxigenic anaerobic cultures and the Xpert C. difficile assay. All specimens displaying discordant results between the Xpert assay and toxigenic culture were sent for Sanger tcdB gene sequencing. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), total concordance rate, and 95％ confidence interval (CI) were calculated before and after resolution of discordant results using SAS 9.3. Results A total of 745 stool specimens were collected and 46 were excluded due to failure of C. difficile recovery. The remaining 699 specimens were included. Compared to the results of toxigenic culture, the sensitivity, specificity, PPV, and NPV of Xpert C. difficile assay were 94.1％ (144/153)(95％CI89.1％-97.3％), 93.2％ (509/546)(95％CI96.7％-99.2％), 79.6％ (144/181)(95％CI72.9％-85.2％)and 98.3％ (509 / 518) (95％CI 96.7％-99.2％), respectively. Both methods had a Kappa of 0.819. Xpert C. difficile assay showed sensitivity of 98.4％(62/63) (95％ CI 90.3％-99.9％) and specificity of 93.2％(509/546) (95％ CI 90.8％-95.2％) for toxin A-negative toxin B-positive strains. After the discordant results resolved by tcdB gene sequencing, PCR assay provided better performance with high sensitivity, specificity, positive predictive value, and negative predictive value [98.8％ (171 / 173), 98.1％ (516 / 526), 94.5％ (171/181) and 99.6％ (516/518), respectively]. Conclusions Compared to the results of toxigenic culture, the sensitivity, specificity and NPV of Xpert C. difficile assay were 94.1％ (144/153) and 93.2％(509/546), respectively. With the results available within 1 h, Xpert C. difficile assay provides prompt and precise laboratory diagnosis in Chinese clinical settings.