Association of serum IL-17 concentrations with disease activity at a single point in time and over time. (A) Correlation of serum IL-17 concentrations with SLEDAI-2k in SLE patients. No significant correlations were observed. (B) Between-visit changes in disease activity (delta SLEDAI-2k) was plotted against between-visit changes in serum IL-17 concentrations (n = 246). No significant correlations were observed. (C) SLEDAI-2k significantly correlated with IL-17/IL-6 ratio in all samples, after removing both undetectable IL-6 and IL-17. Serum IL-17 levels are expressed in pg/ml. IL-17, interleukin-17; SLE, systemic lupus erythematosus; SLEDAI-2k, SLE Disease Activity Index 2000.