Prospective Validation of a Pharmacological Biomarker for Low-Dose Rituximab in Rheumatoid Arthritis

Inclusion Criteria: . Age ≥ 18 years * Diagnosis of rheumatoid arthritis meeting ACR/EULAR 2010 criteria. * Candidates for a Low Dose regimen: on standard dose rituximab and with a good clinical response according to the referring rheumatologist. No maximum duration of use of standard-dose rituximab has been defined. * In the case of co-prescription of csDMARDs (Methotrexate, Leflunomide, Salazopyrine, Plaquenil), the dose must have been stable for 3 months. * If corticosteroids are co-prescribed, the dose should be ≤ 10 mg/d and stable for 3 months. Exclusion Criteria: * Other associated targeted disease-modifying therapy * Sjögren's syndrome or other associated inflammatory rheumatism * Fibromyalgia or other pathology having an impact on the assessment of disease activity * Any active haematological disease affecting lymphocytes (chronic lymphocytic leukaemia, Hodgkin's and non-Hodgkin's lymphomas, lymphoplasmacytic lymphoma, T lymphoma). * Opposition to data processing * No inclusion of persons covered by articles L. 1121-5 to L. 1121-8 and L. 1122-1-2 of the Public Health Code (e.g. minors, protected adults, etc.).