ESR1 and juvenile idiopathic arthritis: The objectives were: 1) to describe the relationship between ESR, CRP, CA2F and its components, and cJADAS27 as index for disease activity in JIA, and 2) to determine if the correlation between predictors of cJADAS27 differ by categories of oligoarthritis (persistent and extended) and rheumatoid-factor negative polyarthritis.