Evaluation of clinical application of two molecular assays for detection of toxigenic Clostridium difficile

Objective In comparison with Xpert C. difficile/Epi through detection of Clostridium difficile toxin genes from clinical stool, the performance of a laboratory-developed (LD) assay was evaluated in detail. Methods A total of 176 stool specimens collected from patients with diarrhea in the First People′s Hospital of Yuhang District and the People′s Hospital of Yingzhou, Ningbo from August 1 to December 30 were detected by the two assays in parallel, and meanwhile the C. difficile strains will be isolated and identified for C. difficile toxin genes by a conventional PCR assay. The Cross-tabs Analysis was used for the results by using SPSS20.0 software. Results In comparison with the results of Xpert C. difficile/Epi as the standard, the LD assay had a sensitivity of 91.7% (22/24), a specificity of 100% (152/152), a positive predictive value (PPV) of 100% (22/22), and negative predictive value (NPV) 98.7% (152/154). The results of two assays were statistically coherent (Kappa=0.950, P<0.001). In comparison with culture and detection of toxin genes results, the LD assay had a sensitivity of 90.0% (18/20), a specificity of 97.0% (152/156), a PPV of 81.8% (18/22), and NPV of 98.7% (152/154)(Kappa=0.838, P<0.001), and the Xpert C. difficile/Epi assay had a sensitivity of 90.0% (18/20), a specificity of 96.0% (150/156), a PPV of 75.0% (18/24), and NPV of 98.7% (150/152)(Kappa=0.792, P<0.001). Conclusions The performance of the LD assay was similar to that of the Xpert C. difficile/Epi kit in detection of toxigenic C. difficile. The LD assay could be directly applied to detection of toxigenic C. difficile from clinical stool samples. The clinical application of this LD assay will also provide a domestic and promising diagnostic assay for diagnosis of C. difficile infection in China.(Chin J Lab Med, 2018, 41: 35-40) Key words: Clostridium difficile; Molecular Diagnostics; Clinical evaluation