Serial measurements of soluble interleukin 2 receptor levels (sIL2-R) in children with juvenile rheumatoid arthritis treated with oral methotrexate

Objective - To investigate the potential clinical utility of serial levels of sIL2-R as a marker of disease activity among children with juvenile rheumatoid arthritis (JRA) treated with methotrexate (MTX). Methods - sIL2-R levels, measured by ELISA, were evaluated in 16 JRA patients (10 polyarticular, six systemic-onset) treated with oral, weekly MTX. sIL2-R values were compared with those of 49 normal controls. Medical record review was used to obtain relevant clinical data. Joint counts (number of swollen joints) were used as indicators of clinical change. A reduction of 50% in joint counts between pre and post treatment measurements was considered a clinically significant response. Results - The mean(SEM) sIL2-R value of pre treatment JRA of 1728(290) U/ml was significantly higher than the post treatment value of 921(229) U/ml (Wilcoxon Rank test, p ≤ 0.001). Pre treatment values were also significantly different from the mean(SEM) of healthy controls of 519(19) U/ml (p < 0.001). Pre treatment sIL2-R levels of 2417(291) U/ml in systemic-onset JRA were significantly higher than sIL2-R values in polyarticular JRA patients of 1218(884) U/ml (Mann-Whitney rank test p < 0.001). Among the 13/16 children with good therapeutic responses (≥ 50% improved), the range of sIL2-R decreases was 154-2641 U/ml (mean 842 U/ml); sIL2-R levels increased in the three children with poor clinical responses to methotrexate. Conclusions - sIL2-R levels paralleled the course of disease in all patients. sIL2-R levels may be useful for monitoring therapeutic responses in children with JRA.