title: A multi-laboratory comparison of two molecular methods for the detection of toxigenic Clostridium difficile.
abstract: BACKGROUND
  Diarrheal disease due to toxigenic Clostridium difficile (CD) accounts for an increased number of hospitalizations and deaths each year. Published guidelines recommend reflex testing of CD antigen-positive samples to molecular testing or testing samples directly by a molecular assay. This multicenter study was designed to compare the accuracy of two different molecular methods targeting different CD genes: Xpert C. difficile Epi RUO RT-PCR assay (XPCR) which targets toxin B (Cepheid, Sunnyvale, CA) and a laboratory-developed PCR (LDPCR) which targets mutations in the tcdC regulatory gene.
  
  
  METHODS
  Two molecular methods for toxigenic CD detection, the Xpert C. difficile Epi RUO RT-PCR assay (XPCR) [Cepheid, Sunnyvale, CA] and a laboratory-developed PCR assay (LDPCR) were compared to a consensus gold standard (CGS) or toxigenic culture (TC) as the reference method. A subset of specimens was subjected to additional molecular characterization of toxigenic CD.
  
  
  RESULTS
  Both molecular methods were >90% sensitive for CD detection. Discordant results were noted when molecular test results were compared to non-molecular methods. Supplemental molecular characterization illustrated inherent difficulties in comparisons using different molecular methods for CD.
  
  
  CONCLUSIONS
  Laboratories may consider using multiple CD detection methods or combinations of methods, including molecular detection for rapid and accurate diagnosis of CD, as driven by best practices for the respective healthcare environment. Laboratories must be aware of intrinsic differences when comparing performance characteristics of different molecular assays.
authors.affiliation: Southeastern Pathology Associates, P.C.Baptist Health, Jacksonville, Florida, United States. diane.halstead@bmcjax.com.
authors.forename: Diane C
authors.initials: DC
authors.lastname: Halstead
authors.forename: Joan
authors.initials: J
authors.lastname: Abid
authors.forename: Lynne
authors.initials: L
authors.lastname: Sloan
authors.forename: Diana
authors.initials: D
authors.lastname: Meza
authors.forename: Daphne
authors.initials: D
authors.lastname: Ramsey-Walker
authors.forename: Donna Jane
authors.initials: DJ
authors.lastname: Hata
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000235:genetics*; D001431:Bacteriological Techniques / Q000379:methods*; D016360:Clostridioides difficile / Q000235:genetics / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000175:diagnosis*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012097:Repressor Proteins / Q000235:genetics*; D012680:Sensitivity and Specificity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D012097:Repressor Proteins; C105615:TcdC protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile