Adherence to etanercept therapy in rheumatoid arthritis patients during 3 years of follow-up.

Objectives: To determine the percentage non-adherence to etanercept in patients with rheumatoid arthritis during three years of follow-up.

Methods: During study visits in this prospective cohort study, blood samples were taken to determine serum etanercept concentrations using ELISA and patients were asked if they had missed an etanercept dose, at which date and for what reason. Non-adherence was defined as serum etanercept concentration <0.