title: Comparison of antigen and two molecular methods for the detection of Clostridium difficile toxins.
abstract: BACKGROUND
  Clostridium difficile (CD) is considered an important cause of diarrhoea associated with the antimicrobial treatment of infections. The pathogenicity of CD is due to toxins A and B, produced by toxigenic CD strains.
  
  
  METHODS
  We evaluated 3 methods for detecting CD toxins: the RIDASCREEN® enzyme immunoassay (EIA) (R-Biopharm)--one detecting toxins directly in the stool specimens and another detecting toxins from isolated CD strains--and 2 molecular methods, the illumigene™ loop-mediated isothermal amplification (LAMP) assay (Meridian) and RIDA®GENE polymerase chain reaction (PCR) assay (R-Biopharm), as direct identification methods from stool specimens. Toxigenic culture (TC) was used as the reference method.
  
  
  RESULTS
  Altogether 884 stool samples were analyzed, of which 253 (29%) were positive by TC. Six hundred and seventy-two specimens were tested by RIDASCREEN EIA, 430 were tested with the illumigene LAMP assay, and 212 were tested with the RIDA GENE PCR assay. CD toxin A and B antigen tests by EIA were very insensitive, both directly from stool specimens (2 series; 57-61%) and in isolated CD strains (53%); consequently the negative predictive value remained low (84-93% and 91%, respectively). Specificity, however, was very good at 98-100%. The 2 molecular methods detected CD toxin genes excellently and equally, resulting in sensitivities, specificities, and positive and negative predictive values of 98%, 100%, 100%, and 98%, respectively.
  
  
  CONCLUSIONS
  Both molecular assays were easy to use, rapid, sensitive, and specific for the detection of toxigenic CD strains.
authors.affiliation: Clinical Microbiology Laboratory, Oulu University Hospital, Oulu, Finland. pirkko.ylisiurua@ppshp.fi
authors.forename: Pirkko
authors.initials: P
authors.lastname: Ylisiurua
authors.forename: Markku
authors.initials: M
authors.lastname: Koskela
authors.forename: Olli
authors.initials: O
authors.lastname: Vainio
authors.forename: Hanna
authors.initials: H
authors.lastname: Tuokko
mesh_terms: D000368:Aged; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification*; D001427:Bacterial Toxins / Q000235:genetics / Q000302:isolation & purification*; D016360:Clostridioides difficile / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D003015:Clostridium Infections / Q000175:diagnosis / Q000382:microbiology; D004768:Enterotoxins / Q000235:genetics / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D008875:Middle Aged; D058889:Molecular Typing / Q000379:methods*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile