P317 Diagnostic accuracy of plasma calprotectin and serum calprotectin in patients with suspected Crohn’s disease

Abstract

Abstract Background Faecal calprotectin is a sensitive marker for chronic inflammatory bowel disease (IBD), and it correlates with the endoscopic disease activity. However, patient reluctance and handling in the laboratory are limitations for the clinical use, and there is a need for new reliable blood-based biomarkers. Prior studies indicate, that serum calprotectin (SCal) and plasma calprotectin (PCal) can be used as biomarkers for IBD, and SCal correlates better with disease activity in Crohn’s disease (CD) than in ulcerative colitis. The aim of this study was to investigate the diagnostic accuracy of SCal and PCal in patients examined for CD. Methods Patients with clinically suspected CD were enrolled in a prospective, blinded, multicentre study examining non-invasive modalities for diagnosing CD (ClinicalTrials.gov identifier NCT03134586). Patients had a standardized work-up including ileocolonoscopy, pan-enteric capsule endoscopy and blood samples within a 2-week period. EDTA plasma was prepared less than 2 hours of sampling by centrifugation at 3000 g for 15 minutes. Samples were stored in a biobank at − 80°C until further analysis. A routine C-reactive protein (CRP) was measured on the same day. SCal and PCal were analysed in batches using the calprotectin assay product nr.1201 from Gentian (Moss, Norway) on the Cobas platform (Roche, Basel, Switzerland). Analyses were performed in an ISO 15189 accredited laboratory. Results 126 patients were enrolled in the study: 69 % women and 31 % men with a median age of 27.5 years (Table 1). A total of 57 (45%) patients were diagnosed with CD based on the result of ileocolonoscopy and pan-enteric capsule endoscopy. Patients with CD had a mean PCal of 0.50 mg/L (95% confidence interval (CI) 0.38-0.62) compared to 0.35 mg/L (CI 0.27-0.44) in non-CD patients (P = 0.03). The mean SCal was 1.45 mg/L (CI 1.20-1.69) and 1.06 mg/L (CI 0.90-1.22) in patients with and without CD, respectively (P = 0.01). Receiver operating characteristics curves showed an AUC of 0.63 (CI 0.53-0.73) for SCal and 0.61 (CI 0.51-0.71) for PCal, which was inferior to CRP (0.76, CI 0.68-0.85, P < 0.02) (Figure 1). In patients diagnosed with CD, SCal and PCal had a moderate correlation with CRP (rs = 0.47 and 0.55, respectively, P < 0.001), and SCal had a weak correlation with the Simple Endoscopic Score for CD (rs = 0.29, P = 0.04) and the Crohn’s Disease Activity Index (rs = 0.36, P = 0.03). Conclusion Levels of PCal and SCal are increased in patients with CD reflecting the systemic inflammatory response in this disease. However, SCal and PCal are insufficient biomarkers in patients with clinically suspected CD, and they are both inferior to CRP.