Association Between Methotrexate Erythrocyte Polyglutamate Concentration and Biological Drug Concentration and Clinical Response in Rheumatoid Arthritis Patients Treated With Subcutaneous Injectable Methotrexate and a First Biological Drug

Inclusion Criteria

• •Age \> 18 years and have social security affiliation.
• •Patients followed in the Rheumatology Department at the hospital of St Etienne.
• •Rheumatoid Arthritis patients in remission (Disease Activity Score 28\<2.6) with methotrexate (MTX) treatment for at least 6months, and with a stable dose for 3months.
• •Patients with a High Disease Activity Rheumatoid Arthritis activity (Disease Activity Score 28\>3.2) with methotrexate (MTX) treatment (≥ 15 mg/week), taking MTX treatment for at least 6months with a stable subcutaneous weekly MTX injection (≥ 15 mg/week) treatment during the previous 3 months.
• •Signed informed consent.