CRP and synovitis: The aims of this study were as follows: (1) to validate a strong association of calprotectin with traditionally used markers of disease activity, (2) to validate a strong association of calprotectin with ultrasound-determined synovitis in a larger cohort, and (3) to determine the predictive value of calprotectin and CRP for clinical disease activity (CDAI index) and power Doppler (PD US) synovitis.