EVALUATION OF 4 COMMERCIALLY AVAILABLE ENZYME IMMUNOASSAYS FOR LABORATORY DIAGNOSIS OF CLOSTRIDIUM-DIFFICILE-ASSOCIATED DISEASES

Four commercial enzyme immunoassays (EIAs) for the detection of Clostr idium difficile toxin A have recently been developed and marketed (Pre mier, Meridian Diagnostics, Cincinnati, Ohio; VIDAS, bioMerierux Vitek , Inc., Hazelwood, Mo.; Tox-A-Test, TechLab, Blacksburg, Va.; and Bart els, Baxter Diagnostics, McGaw Park, Ill.). The performances of these EIAs were compared with those of the tissue culture cytotoxicity assay and a definition of C. difficile-associated disease based on both lab oratory and clinical criteria for 329 clinical specimens. Two EIAs (Pr emier and VIDAS) showed good overall agreement (96 and 95%, respective ly) with the cytotoxicity assay. However, they were less sensitive (84 and 71%, respectively) than the Bartels (94%) or Tox-A-Test (93%) EIA s. The Bartels and Tox-A-Test assays were much less specific, resultin g in poor positive predictive values (56%) of the two assays when comp ared with that of the cytotoxicity assay. Tox-A-Test had the added dra wback of having a significant number of indeterminate results (6.4%). These data indicate that the four EIAs all have specific shortcomings. When using these EIAs, testing strategies that take these shortcoming s into consideration should be developed.