Eligibility Criteria:
Inclusion Criteria:
* Patient with a confirmed Rheumatoid Arthritis according the American College of Rheumatology (ACR) classification criteria (Arnett FC, 1988, Arthritis Rheum)
* Patient with a DAS28 index greater than 3.2.
* Patient eligible for treatment with an anti-TNFα agent (any one of Remicade®, Humira®, Enbrel®, Simponi®, Cimzia®, Remsima®/Inflectra®, Benepali® and Flixabi® according to the "Summary of Product Characteristics" for each product) and Methotrexate combination therapy,
* Patient refractory to treatment with at least one classical DMARDs (one of which has to be MTX) prescribed according to the international recommendations, i.e. for at least 12 weeks at the maximal tolerated dose prior to anti-TNFα treatment and with doses which must have been kept stable during the 4 weeks preceding the initiation of the anti-TNFα therapy. In case of Leflunomide treatment, patients may be included in the study after a period of at least 3 months of Leflunomide stop, or after a washout by cholestyramine for at least 11 days.
* Use of oral steroids (≤ 10 mg/day of prednisone or equivalent dose of another molecule) and/or NSAIDs will be permitted; doses must have been kept stable during the 4 weeks preceding the initiation of the anti-TNFα therapy
* Patient (male or female) at 18 years of age or older at inclusion,
* Negative β-HCG (Human Chorionic Gonadotrophin) pregnancy test, when appropriate, according to the patient's age and contraceptive method.
* Written Informed consent signed from the patient.
Exclusion Criteria:
* Patient having received previously any anti-TNFα biologic therapy or any molecule in development belonging to anti-TNFα class. Patients having received other biologics (such as anti-CD20, anti-CTLA4, IL1 blockers, IL6 blockers and other molecules in development) can be included in the study after a period of at least 6 months,
* Patient non eligible to anti-TNFα according to the SmPC (Summary of Products),
* Patient on anti-TNFα monotherapy without methotrexate,
* Patient with clinically significant, severe and uncontrolled infectious diseases,
* Patient with symptoms of a significant somatic or psychiatric/mental illness,
* Patient with other auto-immune diseases (i.e. Inflammatory Bowel Diseases, Systemic Lupus Erythematosus, vasculitis, uncontrolled asthma, etc.),
* Patient with evidence of cardiac, pulmonary, metabolic, renal, hepatic, gastro-intestinal conditions, which, in the opinion of the Investigator, may interfere with the study,
* Cancer,
* Pregnancy,
* Nursing mothers,
* Patient who is participating in a clinical trial of other biologics or for whom a period of exclusion has been defined