Lower baseline S100A8/9 levels increased the odds of achieving JIA-ACR100 at month 3 by 4.9-fold (95% CI: 1.56–15.24), while the combination of lower S100A8/9 plus lower CRP at baseline increased the likelihood of achieving JIA-ACR100 at month 3 by 6.9-fold (95% CI: 2.20–21.87). This evidence concerns the gene CRP and juvenile idiopathic arthritis.