The purpose of this study is to analyze the frequency of the formation of antibodies against three different anti-TNF biologic agents used for the therapy of juvenile idiopathic arthritis.

Juvenile idiopathic arthritis (JIA) is the umbrella term for a heterogeneous group of inflammatory arthropathies that can affect children and young adults and is the most common rheumatic disease of the pediatric population. In high-income countries it has a yearly incidence of 2-20 cases per 100 000 population and a prevalence of 16-150 cases per 100 000 population. Treatment of JIA includes a combination of pharmacological interventions, physical and occupational therapy, and psychosocial support. Although a definitive cure is still not available, the prognosis for patients with JIA has improved greatly in recent years due to improved disease management and with the introduction of biologics that can provide an efficient alternative for patients who are nonresponsive to other treatments. Traditionally, biologic treatments in JIA have focused on blocking one of the central mediators of the inflammatory response, the cytokine tumor necrosis factor (TNF). Currently there are three anti-TNF agents available for the treatment of JIA: infliximab, adalimumab and etanercept. One of the major drawbacks of these therapeutics is the production of anti-drug antibodies (ADA) that have been correlated with an increased risk of adverse events and loss of drug efficacy. The study will evaluate the frequency of the formation of anti-infliximab antibodies in patients treated with infliximab, anti-adalimumab antibodies in patients treated with adalimumab and anti-etanercept antibodies in patients treated with etanercept. A common practice in cases nonresponsive to one of the described anti-TNF agents is the discontinuation of therapy and switching to a different ant-TNF agent. Therefore, the frequency of the formation of antibodies to each of the described anti-TNF agents will also be compared between patients who have previously received a different anti-TNF agent and patients who have not received any previous anti-TNF therapy. The results of this study will highlight the risks of formation of antibodies to three different anti-TNF biologic agents used for the therapy of JIA either alone or after the previous discontinuation of a different anti-TNF agent.

Inclusion Criteria:

• Clinical diagnosis of juvenile idiopathic arthritis
• Must be treated either with infliximab, adalimumab or etanercept

Exclusion Criteria:

• Contraindications to anti-TNF therapy
• Concurrent treatment with any biologic agent other than infliximab, etanercept, or adalimumab
• Previous treatment with rituximab

primary care clinic