EVALUATION OF A NEW ENZYME-IMMUNOASSAY FOR CLOSTRIDIUM-DIFFICILE TOXIN-A

Aims-To evaluate a new enzyme immunoassay (EIA) method for detection o f Clostridium difficile toxin by comparing it to cytotoxicity assay. T o investigate the nature of false negative and false positive EIA resu lts by evaluating clinical and therapeutic parameters. Methods-737 con secutive diarrhoeal specimens collected fi om patients clinically susp ected of having C difficile colitis were tested for the presence of C difficile toxin by EIA for toxin A and by cytotoxicity assay. Clinical data were evaluated in all cases positive by either method. Results-W ith the cytotoxicity assay as a gold standard, the specificity of EIA for toxin detection was 99.3% and the sensitivity was 62.2%. No false negative ELA specimens were obtained from patients already being treat ed for C difficile colitis. Among patients with cytotoxicity positive specimens, those with EIA positive samples had no clinical features di stinguishing them from patients with EIA negative samples. Conclusions -Although specific, the new EIA method directed against toxin A lacks sensitivity compared to cytotoxicity, False negative EIA tests are not associated with concurrent treatment for C difficile colitis nor with any specific clinical features examined in our study.