Elevated Serum Levels of Calprotectin (Myeloid-Related Protein 8/14) in Patients With Ankylosing Spondylitis and Its Association With Disease Activity and Quality of Life

Background: Calprotectin is one of the major leukocyte S100 proteins showing both calcium binding and antimicrobial characteristics. The serum level of calprotectin is markedly elevated in patients with inflammatory bowel disease, rheumatoid arthritis, as well as systemic lupus erythematosus and has been suggested to play a prominent role in both progression and pathogenesis of these diseases. Aim: The purpose of this study was to investigate the serum level of calprotectin in patients with ankylosing spondylitis (AS) and its association with disease activity and other clinical characteristics of AS. Materials and Methods: Thirty-one patients who met the modified New York criteria for AS and 45 healthy controls were included in this study. Both Bath AS disease activity index and AS disease activity score were applied on the patients with AS for the assessment of disease activity; Bath AS functional index, for the assessment of functional activity; Bath AS radiology index, for the assessment of radiological damage; and the AS quality of life questionnaire for the assessment of disease-related life status. Spinal and hip measurements were performed using Bath AS metrology index. The serum level of calprotectin was determined using enzyme-linked immunosorbent assay kit. Results: Mean serum level of calprotectin was significantly higher in the patients with AS compared with healthy controls (P = 0.003). Serum levels of calprotectin did not correlate with Bath AS disease activity index, AS disease activity score, Bath AS functional index, Bath AS radiology index, Bath AS metrology index, modified Schober, chest expansion, AS quality of life questionnaire, erythrocyte sedimentation rate, and C-reactive protein values (P > 0.05). Conclusions: Our results suggest that calprotectin might play an important role in the pathogenetic mechanisms of AS; however, the calprotectin levels did not correlate with the measurements of disease activity, functional abilities, radiological damage, and the quality of life in these patients. Further insight into this area of research might provide opportunities to develop novel treatment strategies, which take into account the role of these peptides in the pathogenetic mechanisms of AS.