Comparison of eight commercial enzyme immunoassays for the detection of Clostridium difficile from stool samples and effect of strain type.

We compared the performance of 8 Clostridium difficile enzyme immunoassays to cell cytotoxicity neutralization assay and toxigenic culture. The effect of strain type on assay performance was also examined. There were a total of 71 (14.4%) samples in which C. difficile was recovered; 58 (81.7%) of 71 were toxigenic. Compared to a composite reference standard of either C. difficile cytotoxin assay positive or toxigenic C. difficile culture positive, the sensitivities of these assays varied from 31.7% to 55.2%, while the specificities were excellent, ranging from 98.1% to 100%. Among the 57 C. difficile isolates, 30 (51.7%) were of the NAP1 genotype. Stool samples positive for the C. difficile NAP1 strain had a higher positivity rate for the toxin assays.