Usefulness of a novel and rapid assay system for fecal calprotectin in pediatric patients with inflammatory bowel diseases

Background and Aim: Fecal calprotectin (FC) has become a reliable biomarker for intestinal inflammation in inflammatory bowel diseases (IBDs). However, a simple and rapid assay to replace conventional ELISA is necessary for wider use in clinical practice. In this study, we investigated the usefulness of a novel method for measuring FC using a colloidal gold aggregation (CGA) assay for assessing mucosal inflammation in pediatric IBDs. Methods: FC levels were determined by ELISA and CGA assay in 309 fecal samples (ulcerative colitis [UC]: 131; Crohn's disease [CD]: 121; healthy controls: 57). For endoscopic evaluation, the modified Matts' grading system for UC and the simple endoscopic score for CD were used. Results: A strong correlation was found between the FC values determined by the two methods (r = 0.98, P < 0.01). FC levels, determined by CGA assay, strongly correlated with the endoscopic score for UC (r = 0.70, P < 0.01) and CD (r = 0.58, P < 0.01). In the UC patients with endoscopic remission, the FC levels determined by CGA assay (median: 31.5 mu g/g, n = 14) were as low as in healthy controls. For patients in clinical remission but showing an active status endoscopically, FC was more likely to be abnormal than commonly used laboratory markers. Conclusions: Our simple and rapid assay system has excellent performance for assessing mucosal inflammation of IBDs and can be replaced for ELISA. Practical application of this assay system enables us to use FC measurement more widely in clinical practice.