There are limited and conflicting data on the value of serum calprotectin (sCp) in discriminating active from inactive disease activity in ulcerative colitis (UC). Faecal calprotectin (fCp), sCp, serum C-reactive protein (sCRP) and platelets were compared in patients with UC who had clinically active (n = 29) and clinically inactive (n = 42) disease. Serum calprotectin was measured with Bühlmann® (BMN sCp) and ImmunodiagnostikTM (IDK sCp) assays. Median (interquartile range) fCp was higher in active than inactive disease [1004 (466-1922) versus 151 (55-280) µg/g; p < 0.0001). BMN sCp [4534 (3387-6416) versus 4031 (2401-5414) ng/mL; p = 0.1825], IDK sCp [4531 (2920-6433) versus 3307 (2104-4789) ng/mL; p = 0.1065], sCRP [ 4 (2-8) versus 2 (1-4) mg/L; p = 0.0638) and platelets [269 (233-331) versus 280 (227-325) ×10-9/L; p = 0.8055] were similar in active and inactive disease respectively. The area under the receiver operator characteristics curves with 95% confidence limits were 0.85 (0.76-0.94) for fCp, 0.61 (0.47-0.74) for BMN sCp, 0.61 (0.48-0.75) for IDK sCp, 0.69 (0.56-0.81) for sCRP and 0.52 (0.38-0.66) for blood platelets. Faecal calprotectin is the optimum biomarker for discriminating between active and inactive UC. The diagnostic performance of sCp, irrespective of assay, and systemic biomarkers was poor; of these sCRP performed best.
Keywords: Serum calprotectin; faecal calprotectin; serum C-reactive protein ulcerative colitis.