Prediction of Abatacept Discontinuation Using Test Reflecting Immunological Remission in Rheumatoid Arthritis

Inclusion Criteria: * Rheumatoid arthritis (RA) patients (\> pr = 18 years) fulfilling the 2010 ACR/EULAR criteria * Associated to high levels (\> 3 x upper limit of normal in UA/ml) of ACPA measured by the usual anti-CCP(cyclic citrullinated proteins)2 test at the start of abatacept treatment * Receiving IV (intravenous) or SC (subcutaneous) abatacept alone or in combination with a conventional Disease Modyfying AntiRheumatic Drugs (cDMARD) (methotrexate, leflunomide, sulfasalasin in monotherapy or in combination) according to the usual scheme or in tapering phase * Without intra-articular injections of corticosteroids during the last 6 months prior to down-titration of abatacept * Having discontinued corticosteroids at he time of entrance in the study * In deep remission (Disease Activity Score (DAS) 28 ESR (or CRP) \< 2.6 without clinical synovitis) since at least 1 year * In sonographic remission at the time of enrollment (absence of PD (Power Doppler)-positive synovitis on 28 joints defined by a score \< 2 on a 0-3 semi-quantitative scale for each joint) Exclusion Criteria: * Age \< 18 years * RA negative for ACPA (anti-citrullinated proteins antibodies) or not fulfilling ACR/EULAR criteria * Abatacept discontinuation due to serious adverse event, loss of efficacy or pregnancy project