ABSTRACT
BACKGROUND: Clostridium difficile is the most common pathogen of antibiotic-associated diarrhea. Toxigenic strains produce toxin A and toxin B. The pathogenicity of C. difficile is due to the production of these two exotoxins. This study aimed to evaluate diagnostic value of two enzyme immunoassay by comparison of concordance rate to diagnose C. difficile-associated infection. METHODS: C. DIFF QUIK CHEK (TECHLAB, USA) that detect glutamate dehydrogenase antigen and VIDAS C. difficile Toxin A&B (BioMerieux, France) that detect toxin A and toxin B were done in 122 fecal specimens to detect C. difficile. RESULTS: In the total 122 stool specimens, 17 cases showed positive results in both tests. One specimen showed discrepancy that positive result in VIDAS C. difficile Toxin A&B (relative fluorescence value, RFV=2.93) but negative result in C. DIFF QUIK CHEK. Therefore, the concordance rate between two tests was 95.1% (116/122). Both anaerobic culture and in-house PCR for toxin B were negative in the discrepant fecal specimen and there was no clinical evidence that support C. difficile-associated diarrhea, so we concluded result in VIDAS C. difficile Toxin A&B as false positive. CONCLUSIONS: Although these two enzyme immunoassays targeted different antigen, they showed high concordance rate. The discrepant case was concluded to false positive in VIDAS C. difficile Toxin A&B test because it showed negative results in culture and PCR for toxin B and there were no clinical evidences of C. difficile-associated infection. It could be needed for analysis about conditions that cause false positive result in enzyme immunoassays to detect C. difficile toxin.