Potential role of calprotectin as a monitoring biomarker for clinical and sonographic activity and treatment outcome in recent-onset rheumatoid arthritis

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Calprotectin is a protein released during the activation and turnover of leukocytes. It can be used as a biomarker of inflammatory diseases such as rheumatoid arthritis (RA). The current study aimed to measure the serum level of calprotectin in RA patients, recently diagnosed and after initiation of treatment, to determine its association with clinical disease, synovial inflammation determined by Ultrasound (US), and its relation to therapy when compared with other inflammatory markers. A total of 32 patients with recent RA and 20 healthy individuals were assessed for serum calprotectin level (enzyme-linked immunosorbent assay). C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were also measured in patients who were reassessed 4 months after initiation of therapy. Disease activity was evaluated by the disease activity score of 28 joints (DAS28), and US assessment was performed. The mean level of serum calprotectin was significantly higher (P<0.001) than that of controls. At baseline, there were significant (P<0.001) correlations of calprotectin serum level with DAS28, ESR, CRP, grayscale, and power Doppler (PD) synovitis scores. After therapy, all except DAS28 and ESR significantly correlated with calprotectin serum level. Calprotectin was shown to be better (P=0.001) than CRP (P=0.922) and ESR (P=0.104, r2=0.495) in predicting power Doppler synovitis score. Calprotectin results showed higher sensitivity in predicting disease activity at the stage of active inflammation. Serum calprotectin level is strongly associated with clinical, laboratory, and US parameters of inflammation in recent-onset RA. Calprotectin is a confident biomarker for monitoring the treatment outcome in RA patients.