Added Value of Fecal Calprotectin to Support the Diagnosis of Spondyloarthropathies

We read with interest the article by Kopylov, et al , who reported small bowel inflammation consistent with Crohn disease (CD) in 42.2% of patients with spondyloarthropathy (SpA) by video capsule endoscopy1. The link between bowel and joint in SpA has been established for several decades. Already in the 1980s, it was demonstrated that up to 50% of all patients with SpA have microscopic bowel inflammation, without associated gastrointestinal (GI) symptoms2. Calprotectin is a heterodimeric complex of two S100 calcium-binding proteins, myeloid-related protein (MRP)-8 (S100A8) and MRP-14 (S100A9), expressed in granulocytes and monocytes3. Fecal calprotectin (FC) is a sensitive and specific biomarker of intestinal inflammation, and quantification of FC is useful for diagnosis and followup of inflammatory bowel diseases (IBD)4,5. Also in patients with SpA, FC has been shown to reveal GI inflammation before clinical onset6, which was confirmed by Kopylov and colleagues. In daily practice, the diagnosis of SpA based on the Assessment of Spondyloarthritis international … Address correspondence to L. Van Hoovels, Department of Laboratory Medicine, OLV Hospital Aalst, Moorselbaan 164, 9300 Aalst, Belgium. E-mail: lieve.van.hoovels{at}olvz-aalst.be