Table 1.

Performance of four immunoassays compared with the cytotoxin assay for the detection of C. difficile toxins in 200 specimens of feces

Assay methodResultNo. of cytotoxin assay resultsa (n = 200)Performance characteristics (%)
Positive (n = 61)Negative (n = 139)SensitivitySpecificityPPVbNPVc
ImmunoCard Toxin APositive3205210010083
Negative29139
Oxoid Toxin APositive30149999682
Negative31138
TechLab Toxin A/BPositive49180999792
Negative12138
Premier Toxin A&BPositive50182999793
Negative11138
  • a Indeterminate results were initially recorded for five (2.5%) specimens, but these were all resolved on retesting of an appropriate dilution of the stool filtrate.

  • b PPV, predictive value of a positive result.

  • c NPV, predictive value of a negative result.