Evaluation of three commercial tests for the rapid diagnosis of Clostridium difficile-mediated antibiotic-associated diarrhoea: a routine laboratory perspective

Y. Miendje, O. Vandenberg, F. Crockaert, M. Gerard,
A. Dediste, P. Retore, G. Mascart, G. Zissis (Brussels, B)
Objectives: Clostridium difficile is the most important infectious cause of nosocomial diarrhoea in industrialized countries. Early diagnosis is associated with better prognosis, therefore rapid laboratory diagnosis is highly desirable. Therefore, we have compared under routine conditions three commercial Clostridium difficile toxin immunoassays (EIA) (Premier Toxins A&B -Meridian (PTAB), ImmunoCard Toxins A&B — Meridian (ICTAB) and C. difficile Toxin A test — Oxoid (TAO)) allowing a rapid diagnosis of C. difficile associated diarrhoea (CDAD) directly on the stool specimen.
Methods: From January 04 to November 04, all stool samples submitted for routine investigation of C. difficile infection to our hospital laboratory serving four University Hospitals in Brussels, Belgium were evaluated with the 3 EIAs. For comparison purpose, the combination of the culture carried out on cycloserine-cefoxitin-fructose agar and the demonstration of the toxigenicity in cell lines Hep2 performed directly from the stool or from the C. difficile isolate («second look») was considered as the gold standard.
Results: Of the 234 stool specimens from 188 patients included in the study, 25 were found positive (by the toxigenicity assays) for C. difficile, giving an overall recovery rate of 10.7%.
The sensitivity and specificity of the tested methods were respectively, 88% and 97.6% for the PTAB test, 92% and 100% for the ICTAB test and 60.0% and 99.5% for the TAO test. The positive and negative predictive values found were respectively, 81.5% and 98.6% for the PTAB, 100.0% and 99.1% for the ICTAB and 93.8% and 95.4% for the TAO.
Conclusion: These data suggest that the PTAB, ICTAB and TAO assays are acceptable tests for the rapid diagnosis of CDAD due to high negative predictive value but are not equivalent to the cytotoxin assay.
Because, the ICTAB is the most sensitive and specific EIA evaluated, we recommend this test for a rapid screening of patient with nosocomial diarrhoea.
15th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID)
2-5 April 2005 — Copenhagen, Denmark