The correlations of serum interleukin-6 (il-6) levels and serum soluble il-6 receptor levels with disease activity in systemic juvenile idiopathic arthritis patients with and without tocilizumab treatment

Abstract

Results Forty-two SJIA patients, 131 blood samplings were included in this study. Seventeen patients (40%) were treated with tocilizumab during the study. Serum IL-6 levels in patients without tocilizumab treatment significantly elevated in active disease with systemic features and arthritis [median (IQR) = 101.8 (303.2) pg/mL] when compared to active disease with only arthritis [median (IQR) = 4.5 (23) pg/mL], and remission on medication [median (IQR) = 1.5 (0.55) pg/mL], whereas serum IL-6 levels in patients with tocilizumab treatment were not different between groups but there were significantly different when compared to healthy children (p < 0.05). In addition, the correlation between serum IL-6 levels and JADAS-71 in patients without tocilizumab treatment (r = 0.71, p < 0.001) was stronger than patients with tocilizumab treatment (r = 0.42, p = 0.01). Serum sIL-6R levels in SJIA patients with and without tocilizumab treatment were significantly higher when compared to healthy children (p < 0.05). Interestingly, in patients with tocilizumab treatment, serum sIL-6R levels were extremely higher [median (IQR) = 1,110.3 (840.2) ng/mL] than patients without tocilizumab treatment [median (IQR) = 94.2 (82.7) ng/mL]. Conclusion The correlation between serum IL-6 levels and disease activity in patients without tocilizumab treatment was stronger than patients with tocilizumab treatment. In addition, serum sIL-6R levels in patients with tocilizumab treatment were extremely higher than patients without tocilizumab treatment.