• roche logo
  • RMS_Cdiff_banner_interior.png


    cobas® Cdiff Test

    The right result the first time



Molecular detection moves C. difficile testing forward

Traditional methods for identification of Clostridium difficile (C.difficile) include toxigenic culture, which is labor intensive and slow, and enzyme immunoassays (EIA), which have limited sensitivity. Algorithms have been developed using combinations of EIA testing to overcome shortcomings of individual assays.1 However, these algorithms may introduce delays in reporting results to physicians, which adversely impacts patient management. 

Molecular technologies (including nucleic acid amplification tests [NAAT]) offer better sensitivity and turnaround time in identifying toxigenic C. difficile when compared to several other approaches (glutamate dehydrogenase [GDH] assay, toxin A and B immunoassay, cell culture cytotoxicity neutralization assay), either alone or in combination.1

In recent years, the frequency and severity of C. difficile-associated disease has continued to increase, prompting a need for rapid and reliable C. difficile testing, particularly in vulnerable elderly populations. By rapidly detecting C. difficile in patient stool

samples, the cobas® Cdiff Test combines high assay sensitivity with rapid turnaround time and a minimum number of pre-analytic steps, to facilitate earlier intervention of patients suffering from C. difficile-associated disease.

The videos are intended to provide educational information and the opinions of the speakers may not be supported by Roche in their entirety.
The videos are intended to provide educational information and the opinions of the speakers may not be supported by Roche in their entirety.
The videos are intended to provide educational information and the opinions of the speakers may not be supported by Roche in their entirety.

The cobas® Cdiff Test provides the answers that help stop the threat of infection

Test Overview

cobas cdiff test sensitivity and specificity

In a study of >1,200 samples, the cobas® Cdiff Test demonstrated superior performance compared to direct culture cytotoxicity testing.

The performance that clinical confidence demands

The cobas® Cdiff Test delivers sensitivity and specificity that Roche real-time polymerase chain reaction (PCR) can provide.

The cobas® Cdiff Test: 

  • Selectively detects a specific C. difficile toxin gene directly from uniformed stool samples using real-time PCR technology
  • Detects a broad array of toxinotypes and ribotypes
  • Generates robust results automatically, using patented, state-of-the-art algorithms
  • Lower inhibition eliminates the need for repeat testing
  • Adds to the expanded test menu on the cobas® 4800 System, which also includes MRSA/SA testing

Test Performance

Provides confidence in results 

When compared to direct culture cytotoxicity and a molecular method, the cobas® Cdiff Test demonstrated the following sensitivity, specificity, positive predictive values, and negative predictive values:  


Scroll Right
Direct Culture Cytoxicity Comparison*
Sensitivity 97%
Specificity 97%
Positive Predictive Value 83%
Negative Predictive Value 100%
Scroll Right
Molecular Method Comparison*
Sensitivity 95%
Specificity 99%
Positive Predictive Value 94%
Negative Predictive Value 99%

* Performance comparison in a study of >1,200 samples

Inhibition Rate

Make every sample count

When compared to a CE- and FDA-cleared NAAT, the cobas® Cdiff Test had a 4x lower inhibition rate and a 2x lower total error rate. A lower inhibition rate means fewer repeat samples, less chances for error, and better patient care.  

cobas® Cdiff test inhibition rate


cobas® Cdiff test total error rate


Reduce hands-on time with a flexible, automated workflow 

Sample Preparation

Accuracy delivered efficiently 

The cobas® Cdiff Test requires only 3 simple steps for sample prep, minimizing sample handling.  



Hands-on Time

Less hands-on time means more walk-away time 

The cobas® Cdiff Test requires up to 74% less hands-on time than competitor platforms.

Mixed Batch Testing

Run mixed batch assays

The cobas® 4800 System offers flexibility with parallel sample processing capabilities. cobas® Cdiff Test samples can be run with different tests and sample types in one run.

Run mixed batch assays of: 

  • Stool (cobas®  Cdiff Test) 
  • Nasal (cobas® MRSA/SA Test) 
  • Anogenital lesions (cobas® HSV 1 and 2 Test)


In addition to parallel sample processing, the cobas® 4800 System offers an expanding test menu.  


Learn about the system ›




Scroll Right
cobas® Cdiff Assay Performance and Specifications
Sample Type Unformed stool specimen
Sample Processing Simple handling, automated processing on the cobas® 4800 System 
Target Region  C. difficile Toxin B (tcdB)
Contamination Control AmpErase
Internal Control Yes
Analytical Sensitivity 100% (31 toxinotypes detected) 
Analytical Specificity  100% (no cross reactivity across 98 bacteria, virus, fungi)
Clinical Sensitivity* 96.7%
Clinical Specificity*  97.3%
Limit of Detection  225 CFU/mL
Workflow  Mixed batch capability; optimized sample loading

*Compared with direct culture cytotoxicity test 

Intended Use: The cobas® Cdiff Test on the cobas® 4800 System is an automated, qualitative in vitro diagnostic test, that utilizes real-time polymerase chain reaction (PCR), for the direct detection of the toxin B (tcdB) gene of toxigenic Clostridium difficile  in unformed (liquid or soft) stool specimens obtained from patients suspected of having C. difficile infection (CDI). The cobas® Cdiff Test is intended for use as an aid in the diagnosis of CDI in humans in conjunction with clinical and epidemiological risk factors.

  • Acronyms:


1. Surawicz et al. Guidelines for diagnosis, treatment, and prevention of Clostridium difficile infections. Am J Gastroenterol. 2013 Apr;108(4):478-98.