In 54/64 subjects with nosocomial diarrhea, fecal calprotectin levels correlated with the results of stool samples tested for Clostridium difficile toxin gene by PCR. Fecal calprotectin levels can be used as an adjunctive measure to PCR to support the diagnosis of C. difficile infection. Fecal calprotectin (fCPT), found predominantly in neutrophils, is a marker of inflammation in inflammatory bowel disease (IBD) (1) due to neutrophilic infiltration of the gut and shedding into the gut lumen and can therefore be quantified in feces. Serum procalcitonin (sPCT), a biomarker of bacterial infection, has been validated for use in monitoring responses to antibiotic therapy and as a prognosticator of sepsis in critically ill patients (2).We performed a prospective exploratory observational study to assess whether fCPT and sPCT could aid in the diagnosis of Clostridium difficile infection (CDI) in the context of a positive PCR for C. difficile toxin gene (CD-PCR).This study was undertaken at a single tertiary 637-bed university teaching hospital and was approved by the institutional research ethics committee. Inpatients whose stool samples were received for CD-PCR underwent testing for fCPT, as assessed by the two Quantum Blue calprotectin lateral flow rapid tests (Bühl-mann, Basel, Switzerland), according to the manufacturer's instructions. Briefly, a 1:150 dilution of sample with the buffer was centrifuged, and 80 l of the supernatant was loaded onto the test cartridge and placed in the dedicated reader. The assay selectively measures calprotectin by a sandwich immunoassay using monoclonal antibodies. The lower-range assay (LR-fCPT) (range, 30 to 300 g/g) was developed as a screen for IBD, and the higher-range assay (HR-fCPT) (range, 100 to 1,800 g/g) is used to follow IBD therapy and for predicting relapses. As per the manufacturer's recommendations for interpretation with IBD, HR-fCPT values of Ͻ100 g/g represent a mild or noninflammatory state of the gut, whereas values of Ͼ200 g/g indicate active organic disease with inflammation. sPCT levels were measured using the Vidas B.R.A.H.M.S PCT assay (bioMérieux, Marcy l'Etoile, France) on leftover serum from subject samples collected within 48 h prior to the date on which the stool sample was collected for CD-PCR. Written informed consent was obtained from all patients for serum and stool testing and for medical chart review.Chi-square and Fisher exact tests were used to compare categorical variables, and a Student t test was used for continuous variables. Quantitative variables were compared by the nonparametric Mann-Whitney U test and Kruskal-Wallis test. P values of Ͻ0.05 were considered statistically significant. IBM SPSS software (version 22) was used for statistical analysis.Between January and September 2013, 64 subjects (44 CD-PCR positive and 20 CD-PCR negative) were enrolled. There were no significant differences in gender (53% male) and age distribution between the 2 groups; 47 (73%) individuals were Ն60 years old. CD-PCR ϩ cases had a higher mean white cell c...

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