Performance of the artus C. difficile QS-RGQ Kit for the detection of toxigenic Clostridium difficile
Introduction
Clostridium difficile is the most common cause of healthcare-associated diarrhea, and toxigenic C. difficile infection (CDI) accounts for 15% to 25% of all antibiotic-associated diarrheas [1], [2]. CDI has become prevalent and less responsive to treatment worldwide [3], [4]. CDI is associated with considerable morbidity and mortality, which increase healthcare costs [5]. Accordingly, accurate and rapid diagnosis of CDI is essential for proper treatment, infection control, and reduction of healthcare costs.
The diagnosis of CDI is based on both clinical and laboratory findings [2]. The laboratory gold standard for detecting C. difficile is the toxigenic culture (TC); anaerobic culture is followed by confirmation of toxin production by enzyme immunoassay, cell culture cytotoxin neutralization test, or DNA amplification assay [2], [3]. However, TC has limitations such as a long turnaround time and technical complexities [6]. Recently, many laboratories have implemented nucleic acid amplification testing (NAAT) for the direct detection of toxigenic C. difficile. NAAT is highly sensitive and specific and could be used as a stand-alone test although there are some concerns on its single use [7], [8], [9], [10].
The artus C. difficile QS-RGQ Kit (artus C. difficile, QIAGEN, Hilden, Germany) is a newly launched, real-time PCR assay for the detection of toxin A (tcdA) and toxin B (tcdB) genes, and it was evaluated in only one study from Germany [11]. In this study, the diagnostic performance of the artus C. difficile was compared with that of the Xpert C. difficile (Cepheid, Sunnyvale, CA, USA), which was also recently introduced and well-validated [12], [13], [14], [15]. TC was used as a gold standard to compare the performances of both assays.
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Clinical specimens
This in vitro study using remnant stool specimens was approved by the Institutional Review Board of the Konkuk University Medical Center, Seoul, Korea (a tertiary referral hospital with 900 beds). From May to September 2015, a total of 261 loose stool specimens were prospectively collected; these specimens were submitted to the clinical microbiology laboratory for C. difficile testing as a part of routine care. Duplicate specimens from the same patients or specimens with insufficient amount
Results
From the 261 stool specimens, two specimens showed invalid results by the artus C. difficile and one specimen by the Xpert C. difficile. These specimens showed no growth of toxin-producing C. difficile by TC. Excluding these three specimens, 258 specimens were analyzed for performance evaluation. Among 258 specimens, 55 (21.3%) were positive for growth of toxin-producing C. difficile by TC. Sixty seven (26.0%) specimens were positive for the artus C. difficile and 63 (24.4%) for the Xpert C.
Discussion
In this study, we compared the diagnostic performance of the artus C. difficile with that of the Xpert C. difficile, which showed excellent sensitivities (94.4%–100.0%) and specificities (93.0%–98.8%) in previous studies [11], [12], [13], [14], [15], [19]. The performance of the artus C. difficile was comparable to that of the Xpert C. difficile, and the agreement between the artus C. difficile and the Xpert C. difficile was almost perfect (kappa = 0.918). Based on TC, the sensitivity and
Conflict of interest
The authors have no conflict of interest related to this article.
Author contribution
Moon H analyzed the data and wrote the draft; Kim HN and Kim JY collected the specimens and participated in the experiment; Hur M designed this study and finalized the draft; Kim H participated in the experiment; Yun YM reviewed the draft and commented on it.
Acknowledgements
This study was supported by Konkuk University.
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