Comparison of two commercial enzyme immunoassays with cytotoxicity assay and culture for the diagnosis of Clostridium difficile related diarrhea

Summary 184 stool samples were analysed for the presence of Clostridium difficile and toxins using the Meridian Premier Toxin A and TechLab Tox-A EIA kits, selective culture and cytotoxin assay. Of the 184 samples 36 stools tested positive for cytotoxin. tn comparison the sensitivity and specificity of the EIAs and culture were as follows: Meridian, 72 and 87, TechLab, 64 and 95, and selective culture, 83 and 96%, respectively. The positive predictive values and negative predictive values for the various methods were: Meridian, 58 and 93, TechLab, 77 and 92, and selective culture, 83 and 96%, respectively. Discrepant results to those obtained by cytotoxicity assay were encountered with both E1A kits evaluated and less so by culture. In this study direct isolation of Clostridium difficile from stool samples most closely paralleled the findings of the “gold standard” cell line cytotoxicity assay. It appears that a single test for the determination of Clostridium difficile disease is adequate, although a second method improves the predictability of the diagnosis. Direct culture of feces provided a reliable secondary procedure to cytotoxicity assay. The EIAs were simple to use, labour efficient and provided a rapid result. However the lack of sensitivity and relative expense did not justify their routine use in our laboratory.