The French Society of Rheumatology initiated a large national multicenter, longitudinal and prospective cohort, ESPOIR, in order to set up databases to allow various investigations on diagnosis, prognostic markers, epidemiology, pathogenesis and medico-economic factors in the field of early arthritis and rheumatoid arthritis.

The primary objective is to set-up a multicentre cohort of early arthritis (less than 6 months) in France that could serve as a database to studies of various natures.

Specific objectives are in the following domains:

• diagnosis: to help determine among clinical, biological, radiographic and immunogenetics those parameters allowing for the earliest diagnosis classification as possible, in order to target early therapy;
• prognosis: to identify early those patients at risk of severe disease by investigating among clinical, biological, genetic and sociologic factors;
• medico-economic: to identify the costs and their determinants at various disease stage;
• pathologic: to collect a databank of sera, DNA, RNA to allow for studies of transcriptomes and other genomics.

Secondary objectives are twofold:

• to monitor adverse events, particularly rare drug adverse events, in collaboration with other international studies
• to allow access to the data collected in this cohort study in order to facilitate new projects submitted to and approved by the scientific committee.

All patients were referred to each regional center every 6 months during the first 2 years, then every year. Procedures were set up to avoid patients lost to followup as much as possible. At baseline and at each visit, we recorded data for a set of clinical and biological variables recommended for the management of early arthritis. At each visit, rheumatoid arthritis was classified according to the 1987 American College of Rheumatology (ACR) criteria and retrospectively to the 2010 ACR/European League Against Rheumatism (EULAR) criteria.

At each visit, patients completed function and quality-of-life self-administered questionnaires including the Health Assessment Questionnaire-Disability Index (HAQ-DI), Arthritis Impact Measurement Scales version 2 short form, a medico economic questionnaire, and globally assessed disease, pain at rest and pain during motion on a visual analog scale (VAS). Patients underwent radiographs of the hand and wrist (face) and foot (face and oblique). Radiographs were stored in the radiological coordinating center (Brest) and then were evaluated by the van der Heijde-modified Sharp score. Serum, DNA, urine, were collected at baseline. Serum and urine were also obtained at each follow-up visit. They were then sent and stored in adequate and definite conditions in the biological coordinating centre (Paris-Bichat).

Inclusion Criteria:

• patients aged over 18 and under 70
• clinical diagnosis of rheumatoid arthritis as certain or probable
• clinical diagnosis of undifferentiated arthritis potentially becoming rheumatoid arthritis
• at least 2 inflammatory joints since 6 weeks : a swollen joint has to be observed in two articular sites and be present since at least 6 weeks
• arthritis starting since less than 6 months
• never prescribed DMARDS, corticoids, except if less than 2 weeks or except intra-articular injection less than 6 weeks before inclusion
• corticosteroids could be tolerated if prescribed for duration less than 2 weeks in the month before the inclusion with an average dose less than 20 mg per day and stopped two weeks before inclusion

Exclusion Criteria:

• patients aged less than 18 years or aged more than 70 years
• pregnant women
• undifferentiated rheumatism with no potential chance to become rheumatoid arthritis
• other inflammatory rheumatisms clearly defined

A total of 814 patients with early arthritis were included be- tween November 2002 and april 2005.One patient removed his consent form. All the centres were active and each regional centre recruited between 35 and 83 patients.