Effective Detection of Toxigenic Clostridium difficile by a Two-Step Algorithm Including Tests for Antigen and Cytotoxin

Abstract

We evaluated a two-step algorithm for detecting toxigenic Clostridium difficile : an enzyme immunoassay for glutamate dehydrogenase antigen (Ag-EIA) and then, for antigen-positive specimens, a concurrent cell culture cytotoxicity neutralization assay (CCNA). Antigen-negative results were ≥99% predictive of CCNA negativity. Because the Ag-EIA reduced cell culture workload by ≈75 to 80% and two-step testing was complete in ≤3 days, we decided that this algorithm would be effective. Over 6 months, our laboratories' expenses were US$143,000 less than if CCNA alone had been performed on all 5,887 specimens.