Background: Faecal calprotectin (FC) is a good marker in monitoring mucosal healing in adults and children with inflammatory bowel disease (IBD). Its concentrations in faeces is closely related to state of mucosa observed in endoscopy. Due to increasing need in rapid, cheap testing for FC, especially in children, new point-of-care tests (POCT) are being developed. The aim of the study was to compare rapid immunochromatographic test (POCT) with standard enzyme-linked immunoassay (ELISA).
Methods: 20 paediatric patients with IBD (Crohn's disease [CD] 10, ulcerative colitis [UC] 10) were involved in the study and had elective colonoscopy performed. Each patient had FC level measured within a week before endoscopy by two assay (ELISA and POCT). Mucosa status during endoscopy was assessed with Baron score for UC and simple endoscopic score for CD (SES-CD). Full mucosal healing was defined as Baron score or SES-CD of 0. Results of FC were correlated with each other and with endoscopic findings by Spearman's rank correlation coefficient. We have identified two subgroups: those with full mucosal healing, and patients with inflamed gut mucosa. The receiver operating characteristic curves (ROC) were used as a statistical method to establish cut-off points. The area under the curve (AUC) assesses the differentiation quality of the study groups. The Deming regression was used to determine systematic differences between two measurement methods.
Results: Although both FC methods correlated significantly with r=0.66, slope and intercept differed extensively, with up to 3-fold quantitative differences between assays (y = 2.8x − 432). The AUC for the ELISA and POCT was 0.89 and 0.82 respectively. The selected cut-off level of discrimination between subgroup with full mucosal healing vs. subgroup with mucosal inflammation present was 686 μg/g with sensitivity 0.75 and specificity 0.88 for ELISA and 260 μg/g with sensitivity 0.83 and specificity 0.88 for POCT. The ELISA method had stronger, clinically significant correlation with presence of inflammation then POCT with r=0.66 and r=0.55 respectively.
Conclusions: FC is a good marker of mucosal healing in monitoring of children with IBD. Both the POCT and ELISA method showed comparable clinical performance in finding inflammation lesions. However the cut of points for detection of inflammation differed extensively between methods. Further efforts are needed to standardize those two assays.