Background: Several studies have investigated levels of serum TNF-α and IL-6 in patients with juvenile idiopathic arthritis (JIA) with active disease compared to those with inactive disease and healthy controls. However, there is limited information concerning the influence of biological drugs on the serum concentrations of TNF-α and IL-6 during treatment.

Objectives: To determine the dynamics of serum levels of TNF-α and IL-6 in patients with JIA treated with biologic drugs at different time points during treatment and investigate their association with the disease activity.

Methods: We conducted a single-center, bidirectional, observational cohort study in 101 patients with JIA (32 boys, 69 girls, mean age 13.8 years, mean disease duration 7.2 years) treated with biologic drugs. Disease activity was measured by the Juvenile Arthritis Disease Activity Score including 10 joints (JADAS10) and calculated at each patient visit. Clinical examinations and laboratory assessments of serum levels of TNF-α and IL-6 were performed at baseline before starting therapy with biologic drug and in 6 month intervals afterwards up to 2.5 years. Patients in the retrospective group had additional measurements at various longer time intervals up to 10 years after the start of the biologic therapy.

Results: Baseline level of TNF-α before therapy with etanercept or adalimumab was significantly lower than the levels of TNF-α at the 1st and 2nd follow-up measurements during the therapy. The analysis of serum levels of TNF-α in relation to the disease activity states showed the highest mean serum levels of TNF-α in patients on etanercept who had low disease activity state and in patients on adalimumab who had inactive disease. In contrast, the highest mean serum level of IL-6 in patients on tocilizumab was observed in patients with active disease state. The correlation analysis in the total cohort of patients with JIA treated with etanercept or adalimumab showed a weak negative correlation between the serum levels of TNF-α and JADAS10 scores (p=0.007), (r=-0.177). In patients with JIA treated with tocilizumab the correlation analysis between the serum levels of IL-6 and JADAS10 scores revealed a positive correlation (p=0.006), (r=0.448).

Conclusion: The assessment of serum levels of TNF-α in children with JIA during treatment with etanercept or adalimumab is not reliable biomarker of disease activity or immunological remission. In contrast, the serum level of IL-6 in patients with JIA treated with tocilizumab shows positive correlation with disease activity.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: None declared.