P240 Clinical diagnostics of fecal calprotectin: a comparative study of a semi-quantitative rapid test and a quantitative lab test

Abstract Background The non-specific and heterogeneous clinical symptoms complicate the diagnosis of Inflammatory bowel disease (IBD). Colonoscopy, the primary method in IBD diagnostics, is costly and invasive, and not optimal for routine disease monitoring. Fast, user-friendly, and cost-effective diagnostic tests facilitate the timely identification of inflammation and disease monitoring. Calprotectin is a pro-inflammatory protein released by neutrophils at the intestinal mucosa, and detectable in feces. Fecal calprotectin (fCal) is a sensitive biomarker that helps to detect IBD, as its concentration is directly proportional to the degree of intestinal inflammation. Furthermore, fCal analysis helps to confirm disease activity in suspected flares and guides decision-making in drug therapy allocation. Methods In this study the accuracy of fCal detection by the semi-quantitative Actim Calprotectin rapid test and the quantitative automated LIAISON Calprotectin assay was assessed on a panel of 119 clinical stool samples. Actim Calprotectin is a visually interpreted, semi-quantitative dipstick test that is hygienically performed in a single tube. LIAISON Calprotectin is an automated quantitative chemiluminescence immunoassay (CLIA). Analyses were performed at NordLab Oulu clinical laboratory (Oulu University Hospital, Finland). Results fCal testing took only about 15 min of hands-on time with Actim Calprotectin, and 40 minutes with LIAISON Calprotectin. The mean fCal concentration in the 119 analyzed clinical samples was 191.8 μg/g (median 41.9 μg/g; range 0-6,290 μg/g) as quantified by LIAISON Calprotectin. The Actim Calprotectin and LIAISON Calprotectin assays agreed on 94 samples (79.0%) (Figure 1). The fCal concentration range-specific inter-assay agreement was as follows: 81.2% at < 50 µg/g, 65.6% at 50–200 µg/g, and 94.4% at >200 µg/g. The sensitivity of Actim Calprotectin was 94.0% (n=47) for the 50 µg/g cut-off when compared to the quantitative LIAISON Calprotectin. The three samples with fCal concentrations above 50 µg/g in the LIAISON Calprotectin test but interpreted as having fCal concentration below 50 µg/g in the Actim Calprotectin test, had an fCal concentration very close to the 50 µg/g cut-off (< 70 µg/g). Conclusion Actim Calprotectin is a suitable method for fCal detection in a clinical setting, supporting fast disease activity and treatment response monitoring in patients with gastrointestinal inflammation. The rapid test can be utilized for the initial differentiation between negative and positive samples in an outpatient setting, thus helping to limit the use of more laborious quantitative methods to positive samples. Future investigations could focus on evaluating the utility of Actim Calprotectin in routine disease monitoring.