Background: Calprotectin is a protein released during activation and turnover of leukocytes. It could be used as a biomarker of inflammatory diseases, as rheumatoid arthritis (RA).
Aim: The current study aimed to measure 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 ultrasonography (US), and its relation to therapy versus other inflammatory markers. Patients and methods: A total of 32 patients with recent RA and 20 healthy subjects were assessed for serum calprotectin level (ELISA). C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were also measured in patients who were re- assessed 4 months after initiation of therapy. Disease activity was evaluated by the disease activity score of 28 joints (DAS28) and US assessment was performed. Results: The mean level of serum calprotectin was significantly higher (p< 0.001) than the controls. At baseline, there were significant (p< 0.001) correlations of calprotectin serum level with DAS28, ESR, CRP, grey scale (GS) and power Doppler (PD) synovitis scores. After therapy, all except the 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 PD synovitis score. Calprotectin results showed higher sensitivity in predicting disease activity at the stage of active inflammation. Conclusion: Serum calprotectin level is strongly associated with clinical, laboratory and US parameters of inflammations in recent onset RA. Calprotectin is a confident biomarker to monitor the treatment outcome in RA patients.