Evaluation of the cobas cdiff test for detection of toxigenic clostridium difficile in stool samples

Lance R. Peterson, Stephen A. Young, Thomas E. Davis, Zi Xuam Wang, John Duncan, Christopher Noutsios, Oliver Liesenfeld, John C. Osiecki, Michael A. Lewinski

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Nucleic acid amplification tests (NAATs) are reliable tools for the detection of toxigenic Clostridium difficile from unformed (liquid or soft) stool samples. The objective of this study was to evaluate performance of the cobas Cdiff test on the cobas 4800 system using prospectively collected stool specimens from patients suspected of having C. difficile infection (CDI). The performance of the cobas Cdiff test was compared to the results of combined direct and broth-enriched toxigenic culture methods in a large, multicenter clinical trial. Additional discrepancy analysis was performed by using the Xpert C. difficile Epi test. Sample storage was evaluated by using contrived and fresh samples before and after storage at >20°C. Testing was performed on samples from 683 subjects (306 males and 377 females); 113 (16.5%) of 683 subjects were positive for toxigenic C. difficile by direct toxigenic culture, and 141 of 682 subjects were positive by using the combined direct and enriched toxigenic culture method (reference method), for a prevalence rate of 20.7%. The sensitivity and specificity of the cobas Cdiff test compared to the combined direct and enriched culture method were 92.9% (131/141; 95% confidence interval [CI], 87.4% to 96.1%) and 98.7% (534/541; 95% CI, 97.4% to 99.4%), respectively. Discrepancy analysis using results for retested samples from a second NAAT (Xpert C. difficile/ Epi test; Cepheid, Sunnyvale, CA) found no false-negative and 4 false-positive cobas Cdiff test results. There was no difference in positive and negative results in comparisons of fresh and stored samples. These results support the use of the cobas Cdiff test as a robust aid in the diagnosis of CDI.

Original languageEnglish (US)
Pages (from-to)3426-3436
Number of pages11
JournalJournal of clinical microbiology
Issue number12
StatePublished - Dec 2017


  • Active surveillance testing (AST)
  • Clostridium difficile infection (CDI)
  • Health care-associated infection
  • Nucleic acid amplification test
  • Toxin B (tcdB) gene

ASJC Scopus subject areas

  • Microbiology (medical)

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