title: Performance of the artus C. difficile QS-RGQ Kit for the detection of toxigenic Clostridium difficile.
abstract: OBJECTIVE
  Nucleic acid amplification tests are commonly used for the direct detection of toxigenic Clostridium difficile. We evaluated the diagnostic performance of newly launched, artus C. difficile QS-RGQ Kit (artus C. difficile, QIAGEN, Hilden, Germany), in comparison with toxigenic culture (TC) and Xpert C. difficile (Cepheid, Sunnyvale, CA, USA).
  
  
  METHODS
  In prospectively collected 261 diarrheal specimens, the artus C. difficile and the Xpert C. difficile assays were performed. TC using chromogenic agar (chromID CD agar, bioMérieux, Marcy-l'Etoile, France) was used a reference method.
  
  
  RESULTS
  Based on TC, the sensitivity and specificity of the artus C. difficile were 98.2% and 93.6%, respectively, and those of the Xpert C. difficile were 94.6% and 94.6%, respectively; there was no statistical difference. The agreement between the artus C. difficile and the Xpert C. difficile was almost perfect (kappa=0.918). In the artus C. difficile, the cycle threshold (Ct) values of tcdA were constantly lower than those of tcdB in all positive specimens (mean Ct, 24.5 vs. 26.4; mean difference of 1.9). Three specimens were considered tcdA+/tcdB- by the difference of Ct cutoffs between tcdA and tcdB (38.3 and 36.5, respectively).
  
  
  CONCLUSIONS
  The performance of the artus C. difficile is excellent compared with TC and is comparable to that of the Xpert C. difficile. Both PCR assays could be useful diagnostic options for the direct detection of toxigenic C. difficile in clinical laboratories. The optimal Ct cutoff of tcdA and tcdB for artus C. difficile may be further validated in following studies.
authors.affiliation: Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Hee-Won
authors.initials: HW
authors.lastname: Moon
authors.affiliation: Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Hyeong Nyeon
authors.initials: HN
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Republic of Korea. Electronic address: dearmina@hanmail.net.
authors.forename: Mina
authors.initials: M
authors.lastname: Hur
authors.affiliation: Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Heejung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Yeo-Min
authors.initials: YM
authors.lastname: Yun
mesh_terms: D016360:Clostridioides difficile / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D006801:Humans; D057230:Limit of Detection; D021141:Nucleic Acid Amplification Techniques; D011446:Prospective Studies
keywords: Clostridium difficile; Cycle threshold value; Performance; Toxigenic culture; Xpert C. difficile; artus C. difficile QS-RGQ Kit