Evaluation of antibiotic-associated diarrhea with a latex agglutination test and cell culture cytotoxicity assay for Clostridium difficile.

Diagnosis of Clostridium difficile (C. difficile) by its antigen or toxin has improved treatment for patients who have antibiotic-associated diarrhea and opportunistic colonization of the colon with C. difficile. Unfortunately, results from the tissue culture cytotoxicity assay are not available for 48 h. We prospectively compared a latex agglutination test with the tissue culture cytotoxicity assay in 83 patients (15 with antibiotic-associated diarrhea, 23 with non-antibiotic-associated diarrhea, and 45 without diarrhea). In the antibiotic-associated diarrhea group, 43% of patients with pseudomembranes and 25% without pseudomembranes tested positive with both tests. In the non-antibiotic groups 92% with diarrhea and 90% without diarrhea were negative with both tests. The number of discordant results illustrates the value of using two tests to identify C. difficile, since additional patients can be identified by using two tests. We found false positives were rare, and C. difficile toxin or antigen could not be detected in more than half the patients with pseudomembranes. The latex agglutination test for C. difficile is reliable, specific, and faster than the tissue culture cytotoxicity assay. The data suggest that other organisms may also be responsible for pseudomembranous colitis, and that negative tests do not obviate the need for visual evaluation of colonic mucosa in suspected cases of antibiotic-associated diarrhea.