National Cohort of Subjects at Risk of Developing Rheumatoid Arthritis

Inclusion Criteria: * Age between 18 and 80 years old * Group 1: Individuals with high risk of RA (ACPA ≥ 2N or ACPA ≥ N and rheumatoid factor ≥ 2N) and clinical signs of arthralgia (CSA criteria ≥ 4). * Group 2: High-risk individuals (ACPA ≥ 2N or ACPA ≥ N and rheumatoid factor ≥ 2N) without clinical arthralgia (CSA criteria \< 4). * Group 3: First-degree relatives of RA patients (no symptoms, negative controls). * Group 4: Newly diagnosed untreated RA patients (ACPA ≥ 2N or ACPA ≥ N and rheumatoid factor ≥ 2N) (positive controls). Exclusion Criteria: * Groupe1-2-3: • Presence of clinical joint swelling (synovitis) at the time of inclusion and previously noted by a doctor * All groups: * Taking current or past background treatment for RA, even for another indication * Corticosteroid therapy ≥10 mg at baseline and in the previous week * Presence of another connective tissue disease (Sjögren's, dermatomyositis, scleroderma, Sharp syndrome, etc.) * Subject unable to read and/or write * Inability to follow the patient during the study period * Failure to obtain consent * Non-affiliation to a social security scheme, * Persons placed under legal protection, under curatorship or under guardianship * Pregnant or breastfeeding women * Person participating in another intervention research including an * exclusion period still in progress