Evaluation of biosite triage Clostridium difficile panel for rapid detection of Clostridium difficile in stool samples

One hundred two steal samples were tested by both the rapid Triage Clostridium difficile Panel (Triage Panel) and the cytotoxin cell culture assay. Five samples positive by both the C. difficile toxin A (Tox A) and common antigen components of the Triage Panel had cytotoxin titers of greater than or equal to 10,000. Twenty-three samples were Triage Panel Tox A negative but common antigen positive. Ten of these had cytotoxin titers of 10 to 1,000, but 13 were cytotoxin negative. Bacterial isolates obtained from 8 of these 13 specimens were analyzed for Tox A and B genes by PCR, and only two contained toxigenic bacteria. Thus, the majority of samples positive only for C. difficile common antigen contained nontoxigenic bacteria. A Triage Panel Tox A-positive result indicated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 33.3, 100, 100, and 88.2%, respectively. A Triage Panel common antigen-positive result indicated a sensitivity, specificity, PPV, and NPV of 100, 82.7, 53.6, and 100%, respectively. The high NPV of the Triage Panel common antigen, together with rapid reporting of results, should prove useful in avoiding unnecessary use of contact precautions and antibiotic treatment for C. difficile-negative patients. However, with Triage Panel common antigen-positive patients, a sensitive cytotoxin assay should be used to distinguish true cytotoxin-positive patients from C. difficile carriers.