title: Characteristics of Clostridium difficile infection in patients with discordant diagnostic test results.
abstract: BACKGROUND
  Clinical features of Clostridium difficile infection (CDI) cases diagnosed by detection of polymerase chain reaction (PCR), with negative toxin enzyme immunoassay results (EIA) have not been fully elucidated. The purpose of this study was to determine the magnitude of CDI patients who had negative EIA toxin determinations but positive PCR tests, and their differences in clinical presentation.
  
  
  METHODS
  We performed a retrospective study comparing the clinical features of CDI cases detected by EIA (toxins A + B) with cases detected by PCR (toxin negative, PCR positive) over a 16-month period. Only patients with an initial Clostridium difficile infection episode that fulfilled a standardized definition were included.
  
  
  RESULTS
  During the study period, 107 episodes of CDI were detected. Seventy-four patients (69%) had positive glutamate dehydrogenase (GDH) antigen and EIA determinations (EIA positive patients). Thirty-three patients (31%) had GDH positive, negative toxin EIA and positive PCR determination (PCR positive patients). PCR positive patients were younger, 57 (27) years (mean [SD]), than EIA positive patients, 71 (16) years, (p < 0.001). Fewer PCR positive patients were receiving proton pump inhibitors (21 patients, 64%) than EIA positive patients (61 patients, 82%, p = 0.034). The clinical presentation was similar in both groups. In the multivariate analysis, lower age was identified as the only independent variable associated with PCR positive patients.
  
  
  CONCLUSIONS
  One third of Clostridium difficile infection patients present negative toxin EIA and PCR positive tests. Performing PCR determination after the negative EIA test is more relevant in younger patients.
authors.affiliation: Enfermedades Infecciosas, HU Puerta de Hierro, España.
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramos Martínez
authors.affiliation: HU Puerta de Hierro.
authors.forename: Jorge
authors.initials: J
authors.lastname: Ortiz Balbuena
authors.affiliation: Medicina Preventiva, HU Puerta de Hierro.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Asensio Vegas
authors.affiliation: Microbiología, HU Puerta de Hierro.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sánchez Romero
authors.affiliation: Enfermedades Infecciosas (MI), HU Puerta de Hierro.
authors.forename: Elena
authors.initials: E
authors.lastname: Múñez Rubio
authors.affiliation: Medicina Preventiva, HU Puerta de Hierro.
authors.forename: Mireia
authors.initials: M
authors.lastname: Cantero Caballero
authors.affiliation: Enfermedades Infecciosas (MI), HU Puerta de Hierro.
authors.forename: Alberto
authors.initials: A
authors.lastname: Cózar Llistó
authors.affiliation: Microbiología, HU Puerta de Hierro.
authors.forename: Francisca
authors.initials: F
authors.lastname: Portero Azorín
authors.affiliation: Microbiología, HU Puerta de Hierro.
authors.forename: Rocío
authors.initials: R
authors.lastname: Martínez Ruiz
mesh_terms: D000328:Adult; D000368:Aged; D016360:Clostridioides difficile; D003955:Diagnostic Tests, Routine; D003967:Diarrhea / Q000209:etiology; D004761:Enterocolitis, Pseudomembranous / Q000175:diagnosis*; D005260:Female; D005969:Glutamate Dehydrogenase / Q000097:blood; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies
chemical_list: D005969:Glutamate Dehydrogenase