High Percentage of IBD Patients with Indefinite Fecal Calprotectin Levels: Additional Value of a Combination Score

Background and Aim Monitoring mucosal inflammation in inflammatory bowel disease (IBD) is of major importance to prevent complications and improve long-term disease outcome. The correlation of clinical activity indices with endoscopic disease activity is, however, moderate. Fecal calprotectin (FC) is a better predictor of mucosal inflammation, but values between 100 and 250 µg/g are difficult to interpret in clinical practice. We aimed to evaluate the occurrence of indefinite FC levels in a real-life IBD cohort and study the additional value of a combination of biochemical markers and clinical activity indices. Methods In total, 148 Crohn’s disease (CD) and 80 ulcerative colitis (UC) patients visiting the outpatient clinic were enrolled. FC, clinical disease activity scored by the Harvey–Bradshaw index or Simple Clinical Colitis Activity Index, and C-reactive protein (CRP) were assessed. In a subset of patients, endoscopic activity was scored by the simple endoscopic score-Crohn’s disease and Mayo endoscopic subscore. Clinical activity index, CRP, and FC were integrated in a combination score and compared with endoscopy. Results Indefinite FC values were present in 24% of CD and 15% of UC. In the cohort of patients with endoscopy scores available, the combination score predicted endoscopic disease activity in CD with a sensitivity of 83% and specificity of 69% [positive predictive value (PPV) 58%, negative predictive value (NPV) 89%]. In UC, this was 88 and 75% (PPV 93%, NPV 60%). Conclusions A combination of FC with clinical activity indices or CRP may aid in classifying patients with indefinite disease activity according to FC alone.