Salivary Calprotectin is Not a Useful Biomarker to Monitor Disease Activity in Patients with Inflammatory Bowel Disease

Background & Aims: Non-invasive biomarkers are gaining interest for monitoring disease activity in patients with inflammatory bowel diseases (IBD). Fecal calprotectin is a reliable biomarker but patients often report the collection of feces being unpleasant and cumbersome. In this study, we aimed to assess if salivary calprotectin could be used as a non-invasive biomarker to determine disease activity instead of fecal calprotectin. Methods: In this cross-sectional explorative cohort study, stimulated saliva was collected from patients with an established IBD diagnosis and healthy controls. The concentration of calprotectin in saliva was determined by a particle-enhanced turbidimetric immunoassay. Intestinal disease activity was assessed with fecal calprotectin levels and the Harvey-Bradshaw Index (HBI) or Simple Clinical Colitis Activity Index (SCCAI). Missing data were handled using multiple imputation. Results: Sixty-three patients (41 Crohn’s disease and 22 ulcerative colitis) and 11 controls were included. Patients had a mean fecal calprotectin of 138.78 µg/g and a median salivary calprotectin of 1.87 mg/L. No significant correlation was found between salivary calprotectin and fecal calprotectin levels (p=0.495). When patients were stratified in two subgroups based on a fecal calprotectin cut-off value of 250 µg/g, there were no significant differences in salivary calprotectin levels between both patient groups (p=0.641) and between patients and healthy controls (p=0.248). Also, salivary, and fecal calprotectin levels were not significantly different when stratifying patients in two subgroups, active disease and remission, using HBI/SCCAI scores. Conclusions: Salivary calprotectin does not correlate to fecal calprotectin and disease activity scores in patients, making it unreliable for assessing IBD activity.