title: Evaluation of Xpert C. difficile, BD MAX Cdiff, IMDx C. difficile for Abbott m2000, and Illumigene C. difficile Assays for Direct Detection of Toxigenic Clostridium difficile in Stool Specimens.
abstract: BACKGROUND
  We evaluated the performance of four commercial nucleic acid amplification tests (NAATs: Xpert C. difficile, BD MAX Cdiff, IMDx C. difficile for Abbott m2000, and Illumigene C. difficile) for direct and rapid detection of Clostridium difficile toxin genes.
  
  
  METHODS
  We compared four NAATs on the same set of 339 stool specimens (303 prospective and 36 retrospective specimens) with toxigenic culture (TC).
  
  
  RESULTS
  Concordance rate among four NAATs was 90.3% (306/339). Based on TC results, the sensitivity and specificity were 90.0% and 92.9% for Xpert; 86.3% and 89.3% for Max; 84.3% and 94.4% for IMDx; and 82.4% and 93.7% for Illumigene, respectively. For 306 concordant cases, there were 11 TC-negative/NAATs co-positive cases and 6 TC-positive/NAATs co-negative cases. Among 33 discordant cases, 18 were only single positive in each NAAT (Xpert, 1; Max, 12; IMDx, 1; Illumigene, 4). Positivity rates of the four NAATs were associated with those of semi-quantitative cultures, which were maximized in grade 3 (>100 colony-forming unit [CFU]) compared with grade 1 (<10 CFU).
  
  
  CONCLUSIONS
  Commercial NAATs may be rapid and reliable methods for direct detection of tcdA and/or tcdB in stool specimens compared with TC. Some differences in the sensitivity of the NAATs may partly depend on the number of toxigenic C. difficile in stool specimens.
authors.affiliation: Department of Laboratory Medicine, Sanggye Paik Hospital, School of Medicine, Inje University, Seoul, Korea. bmshin@unitel.co.kr.
authors.forename: Bo-Moon
authors.initials: BM
authors.lastname: Shin
authors.affiliation: Department of Family Medicine, Haewoondae Paik Hospital, School of Medicine, Inje University, Busan, Korea.
authors.forename: Sun Mee
authors.initials: SM
authors.lastname: Yoo
authors.affiliation: Department of Internal Medicine, Sanggye Paik Hospital, School of Medicine, Inje University, Seoul, Korea.
authors.forename: Won Chang
authors.initials: WC
authors.lastname: Shin
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D016360:Clostridioides difficile / Q000235:genetics* / Q000302:isolation & purification; D003015:Clostridium Infections / Q000175:diagnosis* / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis* / Q000378:metabolism; D004768:Enterotoxins / Q000235:genetics; D005243:Feces / Q000382:microbiology*; D006801:Humans; D060885:Multiplex Polymerase Chain Reaction; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004768:Enterotoxins; D011933:Reagent Kits, Diagnostic; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile
keywords: Clostridium difficile; Culture; Evaluation; NAAT; Performance