CRP and juvenile idiopathic arthritis: For patients who received MTX (N = 20) and those who did not (N = 5), respectively, the duration of JIA was 4.8 and 4.2 years, 70 and 60 % were rheumatoid factor positive (RF positive), and 55 and 60 % had abnormal (>3 mg/dL) CRP concentrations.