A comparative study was performed to determine the accuracy of Clostridium difficile toxin detection. A commercial cytotoxicity assay (Bartels Immunodiagnostic Supply, Bellevue, Wash.) was compared with conventional microcytotoxicity assays, using Vero and MRC-5 cells. The Bartels system was found to be essentially equivalent to conventional cytotoxicity assays currently being performed for routine C. difficile toxin detection.

The direct immunofluorescence assay (DFA) was compared with culture for test-of-cure analysis for Chlamydia trachomatis in patients 7 to 10 days after antimicrobial therapy was given. DFA test-of-cure results correlated with culture results in 79.5% of 39 patients. Of DFA-negative patients, 97% had negative cultures. Six of seven patients with borderline DFA results had negative culture results.