We assessed diagnostic utility of fecal calprotectin (FC), a biomarker of intestinal inflammation, for Clostridium difficile infection (CDI).
Patients with antibiotic-associated diarrhea (AAD) stratified into severe CDI (n = 50), nonsevere CDI (n = 50), or non-CDI AAD (n = 50) were examined. Stool samples supplied by the hospital diagnostic laboratory were analyzed for calprotectin concentration and for the presence of C. difficile toxin.
Concentrations of FC correlated with severe CDI versus milder CDI or non-CDI AAD (median, 276 μg/g, 11 μg/g, and 16 μg/g, respectively; P = 0.0012). Significant correlations were also demonstrated in CDI caused by binary toxin–producing strains versus CDI caused by binary toxin–negative strains (308 μg/g vs. 53 μg/g, P = 0.016) and with leukocytosis versus no leukocytosis (307 μg/g vs. 16 μg/g, P < 0.0001). Sensitivity and specificity of FC analyzed by receiver operating characteristic curve yielded a sensitivity of 57% and specificity of 88% with an area under the curve of 0.70 (95% confidence interval, 0.62–0.78) for distinguishing CDI from non-CDI AAD and showed FC to have 70% sensitivity and 83% specificity with an area under the curve of 0.84 (95% confidence interval, 0.78–0.90) in distinguishing severe CDI from nonsevere CDI and non-CDI AAD.
Fecal calprotectin may not be elevated in all cases of CDI diagnosed by current hospital standards (enzyme immunoassay or real-time polymerase chain reaction), but its specificity and correlation with disease severity suggest a potential role as confirmatory test in the diagnosis of CDI.