Reasons for inactive disease and flare in systemic onset juvenile idiopathic arthritis patients during tocilizumab treatment.

OBJECTIVES: The aim of our study was to evaluate disease courses and outcomes of sJIA children undergoing tocilizumab (TCZ) treatment, and to establish the predictors which distinguish inactive disease and disease flares. METHODS: Our retrospective study included 48 active sJIA children who were refractory to different anti-rheumatic drugs and who were then started on TCZ. The effectiveness of TCZ was assessed by the changes of sJIA attributed signs and symptoms and the remission was judged according to the Wallace (2004) criteria. RESULTS: The main demographic parameters (Me; IQR) were shown; mean age: 9.9 (5-12.7) years and mean duration of TCZ administration: 27.0 (5.9-89.7) months. During the TCZ treatment 40 cases (83.3%) achieved remission in 138.5 (56.0; 255.0) days. Patients who achieved remission had milder disease course, and presented less frequent epatosplenomegaly, lung, heart involvement and MAS. They had higher Hb and lower WBC, granulocytes, ESR, CRP, LDH, ferritin. The main predictors of achievement of inactive disease, calculated with Cox-regression models, were CRP≤82.0 mg/l (OR=7.9, HR=1.17), ESR≤32 mm/h (OR=17.0, HR=0.85), ferritin ≤273 ng/ml (OR=56.5, HR=2.6), Hb>113 g/l (OR=17.0, HR=1.33), LDH≤676 U/l (OR=113.6, HR=3.2), PLT>335*109/l (OR=5.0, HR=2.5), and intensive depression of WBC in 2 weeks after the 1st TCZ infusion>11% (OR=13.0, HR=6.0) and granulocytes>12% (OR=14.0, HR=4.7). CONCLUSIONS: sJIA children with milder disease course have more posssibilty of achieving disease remission during TCZ treatment. Male sex, signs of high disease activity, previous CS treatment, the long time needed to achieve inactive disease and treatment protocol deviations increased the risk of sJIA flare.