Evaluation of the Clearview Clostridium difficile Toxin A Test and various selective culture media in comparison with the cytotoxin assay for the diagnosis of Clostridium difficile-associated diarrhoea.
OBJECTIVE
Clostridium difficile is the major pathogen associated with nosocomial diarrhoea. We evaluated the performances of a commercially available toxin A enzyme immunoassay (EIA; Clearview C. difficile Toxin A Test), culture and tissue culture cytotoxin assay in the diagnosis of C. difficile-associated diarrhoea.


METHODS
Comparative test performance was determined from data obtained from 166 faecal samples. The initial analysis compared the performance of toxin A EIA and culture with that of cytotoxin assay, this being defined as a 'laboratory gold standard'. A second analysis compared the individual performance of the toxin A EIA, culture and cytotoxin assay using a combined clinical and laboratory diagnostic assessment as a 'clinical gold standard'. In a parallel, study three selective culture media were compared.


RESULTS
From the initial analysis, the sensitivity and specificity of the methods were, respectively, 84.6 and 65.4% for the toxin A EIA, and 38.5 and 93.5% for culture. From the second analysis, the sensitivity and specificity of the methods were, respectively, 100 and 67.5% for the toxin A EIA, 63.6 and 96.7% for culture and 72.7 and 98.0% for cytotoxin assay. Media containing d-cycloserine 250mg/L and cefoxitin 8mg/L performed best, growing 88.2% of the isolates.


CONCLUSIONS
The toxin A EIA we evaluated had poor specificity in the diagnosis of C. difficile-associated diarrhoea. We conclude that in our laboratory the combination of culture and cytotoxin assay is a preferred approach to the diagnosis of C. difficile-associated diarrhoea.
D001427:Bacterial Toxins / Q000032:analysis* / Q000276:immunology; D002478:Cells, Cultured; D016360:Clostridioides difficile / Q000302:isolation & purification*; D003428:Cross Infection / Q000175:diagnosis / Q000382:microbiology; D003470:Culture Media; D004403:Dysentery / Q000175:diagnosis* / Q000382:microbiology; D004761:Enterocolitis, Pseudomembranous / Q000175:diagnosis* / Q000276:immunology; D004768:Enterotoxins / Q000032:analysis* / Q000276:immunology; D005243:Feces / Q000382:microbiology; D006801:Humans; D007124:Immunoenzyme Techniques; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001427:Bacterial Toxins; D003470:Culture Media; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile