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.