Evaluation of a new enzyme immunoassay for Clostridium difficile toxin A.
OBJECTIVE
To evaluate a new enzyme immunoassay (EIA) method for detection of Clostridium difficile toxin by comparing it to cytotoxicity assay. To investigate the nature of false negative and false positive EIA results by evaluating clinical and therapeutic parameters.


METHODS
737 consecutive diarrhoeal specimens collected from patients clinically suspected of having C difficile colitis were tested for the presence of C difficile toxin by EIA for toxin A and by cytotoxicity assay. Clinical data were evaluated in all cases positive by either method.


RESULTS
With the cytotoxicity assay as a gold standard, the specificity of EIA for toxin detection was 99.3% and the sensitivity was 62.2%. No false negative EIA specimens were obtained from patients already being treated for C difficile colitis. Among patients with cytotoxicity positive specimens, those with EIA positive samples had no clinical features distinguishing them from patients with EIA negative samples.


CONCLUSIONS
Although specific, the new EIA method directed against toxin A lacks sensitivity compared to cytotoxicity. False negative EIA tests are not associated with concurrent treatment for C difficile colitis nor with any specific clinical features examined in our study.
Vargas
S O
SO
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Horensky
D
D
Onderdonk
A B
AB
D001427:Bacterial Toxins / Q000032:analysis*; D001681:Biological Assay; D016360:Clostridioides difficile; D004768:Enterotoxins / Q000032:analysis*; D005069:Evaluation Studies as Topic; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D012680:Sensitivity and Specificity; D013048:Specimen Handling
D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile