Real-time polymerase chain reaction correlates well with clinical diagnosis of Clostridium difficile infection

J Hosp Infect. 2014 Jun;87(2):109-14. doi: 10.1016/j.jhin.2014.03.005. Epub 2014 Apr 12.


Aim: To determine the clinical utility of a rapid molecular assay for Clostridium difficile infection (CDI) in an acute hospital setting.

Methods: From March to September 2011, stool specimens from inpatients in two acute hospitals with suspected CDI were tested prospectively by routine cell culture cytotoxin neutralization assay (CCNA), real-time polymerase chain reaction (PCR) using the GeneXpert (Cepheid Inc., Sunnyvale, CA, USA), and a dual testing algorithm [glutamate dehydrogenase (GDH)/toxin enzyme immuno-assay, Premier, Launch Diagnostics, Longfield, UK]. All patients with positive PCR, CCNA or discrepant results were reviewed by a multi-disciplinary team (treating clinician, gastroenterologist, microbiologist and infection control nurse).

Results: C. difficile detection rates were 11.7% (PCR), 6% (CCNA) and 13.8% (GDH). Out of 1034 stool specimens included in the study, 974 (94.1%) had concordant CCNA and PCR results. Eighty-nine percent (886/985) had concordant CCNA, PCR and GDH results, and 94.4% (930/985) had concordant GDH and PCR results. Using clinical diagnosis as the reference, PCR had sensitivity of 99.1%, specificity of 98.9%, positive predictive value (PPV) of 91.9% and negative predictive value (NPV) of 99.9%. CCNA on a single sample had sensitivity of 51%, specificity of 99.4%, PPV of 91.9% and NPV of 94.3%. GDH had sensitivity of 83.8%, specificity of 94.5%, PPV of 64.7% and NPV of 97.9%. Almost twice as many patients were positive by PCR compared with CCNA (121 vs 62); 54/59 of those with discrepant results were clinically confirmed as CDI.

Conclusion: Rapid diagnosis of CDI using PCR was timely, accurate and correlated well with clinical diagnosis.

Keywords: Cell culture cytotoxin neutralization assay; Clinical diagnosis; Clostridium difficile; Glutamate dehydrogenase; Polymerase chain reaction; Toxin enzyme immuno-assay.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Clostridioides difficile / isolation & purification
  • Clostridium Infections / diagnosis*
  • Clostridium Infections / microbiology
  • Diarrhea / diagnosis*
  • Diarrhea / microbiology
  • Female
  • Humans
  • Immunoassay / methods
  • Male
  • Middle Aged
  • Molecular Diagnostic Techniques / methods*
  • Predictive Value of Tests
  • Prospective Studies
  • Real-Time Polymerase Chain Reaction / methods*
  • Sensitivity and Specificity
  • United Kingdom
  • Young Adult