Clinical Research Directory

Inclusion Criteria: * The patient must have given their free and informed consent and signed the consent form * The patient must be a member or beneficiary of a health insurance plan * The patient is at least 18 years old * The patient has rheumatoid polyarthritis as defined by the ACR-EULAR 2010 criteria, treated orally or subcutaneously with MTX for at least 3 months with a stable (unchanged) dosage for at least 1 month, and a stable (unchanged) route of administration for at least 1 month. And no planned change in Methotrexate intake at least until the second study visit. Other treatments at the same time are authorized Exclusion Criteria: * The subject is participating in an interventional study, or is in a period of exclusion determined by a previous study * The subject refuses to sign the consent * It is impossible to give the subject informed information * The patient is under safeguard of justice or state guardianship * The subject has a contraindication to taking methotrexate (including a patient with a desire to become pregnant).