Objectives To test the hypothesis that calprotectin is associated with clinical and ultrasound disease activity in patients with RA in a cross-sectional study and to investigate the contribution of various parameters to predict ultrasound findings. Results We found that DAS28 (r=0.605, p<0.001; r=0.605, p<0.001, resp.) and CRP levels (r=0.451, p=0.006; r=0.463, p=0.004, resp.) correlate significantly with GS and PD synovitis.
In addition, calprotectin correlated significantly with PD synovitis (r=0.497, p<0.005). Furthermore, serum calprotectin significantly correlated with CRP (r=0.629, p<0.001) and DAS28 (r=0.385, p<0.019).
In addition to DAS28 (p=0.001), calprotectin (p<0.001) was a strong predictor of active PD synovitis (adjusted R2=0.811). Conclusions This study confirms tight association between clinical, laboratory and ultrasound assessment and support circulating calprotectin as an important biomarker for monitoring synovial inflammation in RA.