Evaluation of a real-time PCR assay for the qualitative detection of Clostridium difficile toxin gene and its clinical application

Objective In comparison of the performances for the detection of Clostridium difficile toxin B genes from stool between BD MAX Cdiff assay and a laboratory-developed (LD) assay.The LD assay was evaluated in clinical application. Methods This study was a clinical application research. A total of 147 stool specimens from patients with diarrhea in Hangzhou First Hospital affiliated with Zhejiang Chinese Medical University were detected by the two assays from 1 July to 30 September 2014. DNA extraction and amplification of the tcdB gene were performed automatically on the BD MAX platform. Meanwhile, the tcdA and tcdB gene were detected by the LD real-time PCR assay after DNA extraction. Then, the results were analyzed by use of SPSS 10.0. Results A total of 147 stool samples were collected. There were 33 C. difficile positive cases and 114 negative cases detected by both of two assays. However, there were four stool samples had incongruent results. In comparison with BD MAX, the LD assay had a sensitivity of 93.94% (31/33), a specificity of 98.25% (112/114), a positive predictive value of 93.94% (31/33), and negative predictive value 98.25% (112/114). Furthermore, the results of the LD assay were statistically coherent with that of the BD assay (Kappa=0.922, P<0.01). Conclusions The LD assay was highly sensitive and accurate as BD MAX Cdiff assay in the detection of toxigenic Clostridium difficile. Furthermore, this LD assay could be also applied to detection of clinical stool samples directly with low cost. The assay will be more promising in diagnosis of toxigenic C. difficile in clinical application in China due to no additional instrument needed.(Chin J Lab Med, 2017, 40: 511-514) Key words: Clostridium difficile; Bacterial toxins; Molecular diagnostic techniques