Is there any value in measuring faecal calprotectin in Clostridium difficile positive faecal samples?

Markers of intestinal inflammation have been proposed for inclusion in Clostridium difficile diagnostic algorithms. Faecal calprotectin (f-Cp), a sensitive marker of intestinal inflammation, was evaluated for utility in C. difficile diagnosis in the hospital setting. One hundred and twenty C. difficile positive and 99 C. difficile negative faecal samples of hospital-acquired diarrhoea were analysed for f-Cp using a quantitative ELISA. C. difficile positivity was confirmed using ELISAs for either toxins (n=45) or glutamate dehydrogenase (GDH) with toxin gene confirmation (n=75). Non-parametric ANOVA (Kruskal-Wallis) was used for data analysis. C. difficile positive samples had higher (P<0.05) median (interquartile range) f-Cp levels; 336 mu g g(-1) (208-536) for toxin and 249 mu g g(-1) (155-498) for GDH and toxin gene positive compared with 106 mu g g(-1) (46176) for C. difficile and culture-negative faecal samples. Five C. difficile positive samples were f-Cp negative (<50 mu g g(-1)). A f-Cp concentration >50 mu g g(-1) was 96% sensitive and 26% specific for C. difficile, with area under the ROC curve of 0.82. There is no role for f-CP alone in predicting C. difficile infection in hospital-acquired diarrhoea due to its low specificity.