P615 Improving IBD monitoring by understanding preanalytical faecal calprotectin variability

Abstract

Abstract Background Currently, faecal calprotectin (fCal) is considered the best available biomarker for both diagnosing and monitoring IBD. However, little is known about the stability of this protein in stool: The few studies available are contradictory. Our aim was to investigate the pre-analytical and biological variability of fCal in order to provide tools for its interpretation in the clinical setting. Methods Samples from 36 patients with IBD were collected to verify the preanalytical stability of fCal. Aliquots of homogenised stool were stored at room temperature and 37°C and fCal concentration measured for 7 consecutive days. In addition, fCal stability was assessed at each respective temperature in assay-specific extraction buffer. Results Baseline fCal concentration in stool samples varied from 14 to 2210µg/g. In aliquots or raw stool samples kept at room temperature, mean change from baseline on days 1, 4 and 7 was -30,95%, -43,66%, and -58,68%, respectively. This decline was irrespective of fCal concentration at baseline, but significantly reduced by using an assay-specific extraction buffer (Fig.1). Figure 1. Conclusion fCal is not stable at room temperature. Patients with IBD and their carers may be falsely reassured by low calprotectin values. Our results indicate that for preanalytical fCal handling, samples should only be stored at room temperature in the short term (up to 24 h). While refrigeration may be suitable for up to 48 h, the use of special extraction fluids improves fCal stability for a longer period. The sending of stool samples by post should therefore be avoided unless extraction buffer is used.