Univariate logistic regression model revealed that the number of joints showing synovitis on US at baseline (P=0.001, OR=1.489, 95%CI: 1.189–1.865) and CRP (P=0.003, OR=1.064, 95%CI: 1.021–1.108) predicted higher ACRpedi 50 response, while systemic JIA subtype (P=0.032, OR=0.222, 95%CI: 0.056–0.877) predicted lower ACRpedi 50 response (Table 4). Here, CRP is linked to synovitis.