Improving IBD diagnosis and monitoring by understanding preanalytical, analytical and biological fecal calprotectin variability

BACKGROUND: The appropriate clinical use of fecal calprotectin (fCal) might be compromised by incomplete harmonization between assays and within- and between-subjects variability. Our aim was to investigate the analytical and biological variability of fCal in order to provide tools for interpreting fCal in the clinical setting. METHODS: Experiments were conducted to investigate the effects of temperature and storage time on fCal. Thirty-nine controls were enrolled to verify biological variability, and a case-control study was conducted on 134 controls and 110 IBD patients to compare the clinical effectiveness of three different fCal assays: ELISA, CLIA and turbidimetry. RESULTS: A 12% decline in fCal levels was observed within 24 h following stool collection irrespective of storage temperature. Samples were unstable following a longer storage time interval at room temperature. Within- and between-subjects fCal biological variability, at 31% and 72% respectively, resulted in a reference change value (RCV) in the region of 100%. fCal sensitivity in distinguishing between controls and IBD patients is satisfactory (68%), and the specificity high (93%) among young (