Comparative Evaluation of Six Commercially Available Assays for the Detection of Clostridium difficile Toxins in Fecal Specime

Clostridium difficile is the primary cause of nosocomial diarrhea and pseudomembranous colitis. Recent evidence suggests an increasing role for the organism as an agent of community-acquired infection, and characterization of increased virulence and antibioticresistance (particularly to fluoroquinolone agents) among certain strains is troubling. With protocols for treatment and containment increasingly complicated, early diagnosis becomes key to successful epidemiologic strategies. We evaluated seven commercially available assays designed to detect either toxin A and/or toxin B associated with C. difficile-associated disease (CDAD). Results of the seven assays were compared to cell culture cytotoxicity, recognized as the gold standard for the laboratory detection of CDAD. Three hundred fresh fecal specimens were tested yielding a positivity rate of 11% by cell culture cytotoxicity. Sensitivity, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) for each assay are tabulated.