VIDAS C. difficile toxin A&B assay performance evaluation and epidemiological analysis of samples collected in UK and US
Abstract number: P1379
Foussadier A., Rolland D., Bridon L., Rice B., Brazier J., Hall V., Young S., Smith R., Dumas N., Amphlett M., Nancekievill K., Delaney C., Apcar S.
Objective: Evaluate the performance for the VIDAS C. difficile Toxin A&B test (CDAB): sensitivity and specificity compared to the Gold Standard Cytotoxicity Assay (CTA) and assay precision. Positive samples collected were further identified by ribotyping.
Methods: Precision was determined at 3 sites: the 6 samples were tested in duplicate, in 2 runs per day, with each of 2 VIDAS CDAB reagent lots in 3 sites over a period of 6 days. Sensitivity and specificity were determined during a clinical trial where over 1000 samples were collected from 2 sites, one in the US and one in UK in order to have a representative collection of 100 positive samples. Fresh stool sent to the laboratory for suspicion of diarrhoea due to C. difficile were tested in parallel with VIDAS CDAB and CTA assays. ROC curve analysis was performed to validate the cut-off established during the development of the assay. C. difficile strains were isolated from the positive samples and submitted for PCR ribotyping and identification.
Results: Analysis of the precision study results show the CV's for total precision are less than 12% for all panel members excepted for the negative sample. Sensitivity of VIDAS CDAB compared to CTA was 88.3%. Specificity of VIDAS CDAB compared to CTA was 99.8%. The PPV was 98.1% and the NPV was 98.4%. The ROC curve analysis confirmed the choice of the assay cut-off and equivocal zone. Ribotyping results of over 87 positive samples are presented according to their geographical origins: ribotype 017(2%), ribotype 027(30%), ribotype 106(16%).
Conclusion: The total precision for the VIDAS CDAB test was <12% and indicate a precise pre-analytical stool processing method. The sensitivity and specificity of the VIDAS CDAB test in comparison to CTA was 88.3% and 99.8% respectively. The VIDAS CDAB test has the ability to detect different strains of C. difficile, including the strains 017 and 027, which are very important for the epidemiology and treatment of C. difficile associated disease.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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