A two-step algorithm for the diagnosis of Clostridium difficile infection: screening with a rapid immunoassay for the detection of glutamatedehydrogenase and toxinsAandB followed by a real-time PCR for C.difficile
Abstract number: P680
Introduction: The Techlab ® C. diff Quik Chek Complete (Techlab Blacksburg, VA, USA) is a rapid immunoassay for the detection of Glutamatedehydrogenase and toxins A and B in fecal specimens, using specific antibodies. The BD Gene-Ohm Cdiff (BD Diagnostics, San Diego, CA, USA) is a real-time PCR assay targeting the toxin B gene (TcdB) of Clostridium difficile with a fluorogenic target-specific hybridization probe for the detection of the amplified DNA. With toxigenic culture (TC) as gold standard, we evaluated the performances of the combination of these tests for the diagnosis of C. difficile infections (CDI) on stool specimens.
Materials and Methods: Stools were from inpatients of the St Luc-UCL University hospital (890 beds), older than 2 years and suffering from diarrhoea. Cell cytotoxicity (CTA) was performed on MRC5 cells. Cultures were performed on CCFA. In case of positive culture and negative CTA, colonies were tested for 'in vitro' toxin production (TC). Some cultures were repeated on CCFA with added taurocholate (TCCFA). Real-time PCR and the rapid immunoassay were performed according to the manufacturer's instructions.
Results: A total of 607 stool specimens collected in 2008 were tested. Eighty four samples were shown to contain toxigenic C. difficile by CTA and/or toxigenic culture (prevalence: 13.9%). The sensitivity, specificity, PPV and NPV of BD Gene-Ohm Cdiff were respectively: 91.7%, 96.5%, 81.1% and 98.5%. Those of CTA were 69.0%, 100%, 100% and 95.3%. Unresolved result was recorded in 2 instances. PCR tests were repeated, the two results remained unresolved and were excluded from our calculation. Screening with C. diff Quik Chek Complete followed by the BD Gene-Ohm Cdiff on GDH positive, toxins A and B negative samples gave sensitivity, specificity, PPV and NPV of respectively: 91.5%, 99.0%, 93.8% and 98.7%.
Conclusion: The combination of theTechlab ® C. diff Quik Chek Complete and the BD Gene-Ohm Cdiff demonstrated a very good sensitivity much superior to that of CTA and a good specificity. It is a rapid method allowing result in less than two hours.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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