The purpose of the present study is to assess the measurement properties of a tolerability questionnaire. The results obtained in patients with Rheumatoid Arthritis (RA) being treated will be robust and will assess the patient's tolerability to the treatment. Patients with greater tolerability will be more satisfied with their treatment.

Clinicians do not have any standardized questionnaire to assess the tolerability from the patient's perspective. The tolerability assessment of the different pharmacological strategies for Rheumatoid Arthritis, from the patient's perspective, would provide additional information, improve doctor-patient communication and improve both adherence to and efficacy of treatment. For these reasons, the development and validation of a new tool is necessary not only for future researches, but for use in standard clinical practice.

The first phase of the development of the questionnaire has already been completed. The second phase of the development of the questionnaire has been designed at to validate the tool in the Spanish population.

This study aims to assess the measurement properties of a new tool which assesses the impact of daily life in Rheumatoid Arthritis.

Inclusion Criteria:

1. Patients over 18 years old.

2. Patients with RA diagnosed according to the standards of the ACR (American College of Rheumatology) in 1987 or to the ACR/EULAR in 2010

3. Patients on treatment with any Rheumatoid Arthritis drug for at least 3 months before their inclusion in the study *

4. Patients who have provided informed consent prior to taking part in the study.

   • It's not necessary for patients to be treated in first-line at the moment of the inclusion in the study.

Exclusion Criteria:

1. Patients with rheumatic disease other than Rheumatoid Arthritis. Will be exclude patients with the following concomitant diseases: Rheumatic autoimmune disease other than RA; Functional Class IV as defined by the ACR Classification of Functional Status in Rheumatoid Arthritis; Diagnosis of juvenile idiopathic arthritis; inflammatory joint disease other than Rheumatoid Arthritis.
2. Patients with any other concomitant disease or treatment that, under clinical criteria, could affect the results of the study or any major episode of infection or disease requiring hospitalization.
3. Patients with any other medical or physiological condition that, in the view of the investigator, could compromise the ability of the patient to answer the study questions.
4. Patients who participated in interviews of the Phase I (development of the questionnaire)

Patients diagnosed with Rheumatoid Arthritis