COMPARISON OF VIDAS CLOSTRIDIUM-DIFFICILE TOXIN-A ASSAY AND PREMIER CLOSTRIDIUM-DIFFICILE TOXIN-A ASSAY TO CYTOTOXIN-B TISSUE-CULTURE ASSAYFOR THE DETECTION OF TOXINS OF CLOSTRIDIUM-DIFFICILE

Damage to the intestinal mucosa by Clostridium difficile (CD) is toxin mediated. Two enzyme immunoassays (EIAs) for toxin-A detection, the a utomated Vitek immunodiagnostic assay system CDA (VIDAS CDA), and the Premier toxin A (Premier) were tested for their ability to detect toxi n A in 301 stool samples and compared with an in-house tissue culture assay for toxin B (TCA). Of these 301 samples, 49 were TCA positive an d 252 were TCA negative. Agreement between VIDAs CDA and TCA on the in itial run was 85% (255 of 301) and increased to 94% (278 of 296) when discordant samples were retested from available frozen specimens. Corr esponding levels of agreement for Premier were 91% (272 of 301) and 98 % (284 of 288), respectively. If tissue culture positivity at any tite r was used as the sole criterion for positivity of the specimen, agree ment with positive TCA before and after repeat testing was 57% (26 of 49) and 74% (34 of 46) for VIDAs CDA and 65% (32 of 49) and 95% (36 of 38) for Premier. Agreement with negative TCA titers was good: 90% for VIDAs CDA and 95% for Premier, and 98% for VIDAS CDA and 99% for Prem ier after repeat testing. Predictive values positive and negative afte r repeat testing were, respectively, 88% and 96% for VIDAs CDA, and 95 % and 99% for Premier. Results for the automated and manual EIA method s for detection of C. dffficile toxin A were obtained in 2.5 h as comp ared with 36-48 h for tissue culture.