Comparison of culture, cytotoxin assay, two enzyme-linked immunosorbent assays and the polymerase chain reaction in the laboratory diagnosis of Clostridium difficile-associated disease

Two hundred faecal specimens submitted for Clostridium difficile testing were examined for: presence of C. difficile by culture, cytotoxin activity in cell tissue culture, detection of toxin A by Premier enzyme immunoassay (EIA), detection of toxins A and B by Cytoclone EIA, and for the presence of gene sequences encoding toxins A and B by the polymerase chain reaction (PCR). Sixty-three (31.5%) were positive in one or more tests of which 33 (16.5%) were positive in all tests. Sensitivities and specificities were respectively: culture 97%, 94.5%; cytotoxin assay 94.5%, 97%; Premier 100%, 97.5%; Cytoclone 100%, 97.5% and PCR of toxin genes A and B (which gave identical results) 97% and 96.5%. EIA gave the best results achievable within one day. Culture failed to distinguish toxigenic from non-toxigenic strains, while PCR failed to prove if toxigenic strains were producing toxin in vivo.