Original ArticlePerformance evaluation of the Verigene® Clostridium difficile nucleic acid test, an automated multiplex molecular testing system for detection of C. difficile toxin
Introduction
Clostridium difficile infection (CDI) is the leading cause of antibiotic-related diarrhea, and its incidence is increasing in both community and healthcare settings [1]. CDI recurrences after treatment often occur and severe cases require early and appropriate therapies, including surgery [2], [3], [4]. Furthermore, CDI outbreaks may occur due to transmission of C. difficile between persons who are using any antimicrobials and are at risk of C. difficile colonization [5], [6], [7], [8]. Therefore, an accurate diagnosis is necessary for effective treatments and infection control.
Although toxigenic culture and cell cytotoxicity assays are gold standards for the detection of toxigenic C. difficile, they are time-consuming and require special equipment and trained microbiologists, and are therefore difficult to perform routinely [9]. In contrast, enzyme immunoassays (EIAs) are simple and can be performed rapidly. EIAs for the detection of glutamate dehydrogenase (GDH), which is produced by C. difficile, are highly accurate compared with culturing methods [10].
Polymerase chain reaction (PCR) can be used to detect toxin genes with high sensitivity [11], [12], [13]. The Verigene® Clostridium difficile nucleic acid test (Verigene® CDF test) can detect tcdA, tcdB, binary toxin genes, and the single nucleotide deletion at base pair 117 in the tcdC gene which is used to differentiate the 027/NAP1/BI strain automatically and rapidly. Although previous reports have confirmed the efficacy of the Verigene® CDF test, its performance has not been fully evaluated, and only a few studies have compared it to EIAs [14], [15], [16]. Furthermore, geographic variability in pathogenic strains causing CDI exists, and differences in the epidemiology and medical settings affect the performance of diagnostic methods [10], [17], [18]. Therefore, we compared the Verigene® CDF test with EIAs which were used as a routine method, based on the results of toxigenic culture as a reference method for the detection of C. difficile toxin.
Section snippets
Study design and sample collection
This study was performed between June 2015 and February 2016. We tested 118 stool samples submitted to our laboratory for diagnosis of CDI. We simultaneously performed two EIAs and the Verigene® CDF test. Toxigenic culture was performed immediately or afterward using the samples stored at −80 °C. We did not obtain informed consent because samples were anonymized and the data did not include other patient information. The institutional review board of Nagasaki University Hospital approved the
Concordance among EIAs and Verigene® CDF test
The numbers of concordant and discordant results among four assays of C. DIFF QUIK CHEK COMPLETE, X/Pect Toxin A/B, Verigene® CDF test, and toxigenic culture were presented in Table 1. The overall concordance rates were 81.4% (96/118), 78.8% (93/118), and 90.7% (107/118) between C. DIFF QUIK CHEK COMPLETE and the Verigene® CDF test, X/Pect Toxin A/B and the Verigene® CDF test, and C. DIFF QUIK CHEK COMPLETE and X/Pect Toxin A/B, respectively.
The performance of EIAs and the Verigene® CDF test for detection of C. difficile toxin
The sensitivity of the Verigene® CDF test (93.9%) was
Discussion
In this study, we assessed the diagnostic accuracy of the Verigene® CDF test for the detection of C. difficile toxin directly from stool samples. Our results indicated that the performance of the Verigene® CDF test, particularly its sensitivity, was better than that of the two EIAs. Although EIAs for toxin detection are easy and fast to use, their low sensitivity is problematic. Yuhashi et al. reported that 48.3% of negative stool samples evaluated with EIAs gave false negative results [19].
Additional information
This work was presented as a poster at the ASM microbe 2017.
Conflict of interest and funding
Reagents, instrumentation, and funding were provided by Hitachi High-Technologies Corporation (Tokyo, Japan).
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