The French Society of Rheumatology has initiated a large national multicenter, longitudinal, prospective follow-up of patients presenting with early inflammatory back pain in order to set up a database to facilitate several investigations on diagnosis, prognosis, epidemiology, pathogenesis and medico-economics in the field of early inflammatory back pain and spondyloarthritis.

Patients were recruited if they had inflammatory back pain of more than 3months and less than 3years. Patients will be followed every 6months during the first 2years then every year during at least 5years. Apart from information collected on a Case Report Form (demographics, disease activity, severity, co-morbidities, socio-economics, treatments, radiological and MRI evaluation of the spine and the pelvis according to the local investigators, and for some centers bone densitometry and ultrasonography of entheses), the digital X-rays and MRI of the spine and pelvis are stored using a specific software (Carestream) and the biological samples (DNA, RNA, sera, urines) are centralized at the Biological Resources Center (Bichat Hospital).

The recruitment period of the 708 patients (mean age: 34±9years, female 54%, HLA-B27 positive: 57%) in the 25 centers was 26months (from December 2007 to April 2010). The modified New York criteria, Amor criteria, ESSG criteria and axial ASAS criteria were fulfilled by 26%, 77%, 76% and 67% of the patients at entry, respectively. A history or current symptoms suggestive of peripheral arthritis, acute anterior uveitis and inflammatory bowel disease were observed in 21%, 9% and 4% of the patients, respectively. The disease was active (BASDAI: 45±20) despite an NSAID intake in 66% of the patients.

This large cohort should facilitate the conduct of researches in different areas (clinical, medico-economics, translational) in order to improve our knowledge on the pathogenesis and natural history of axial spondyloarthritis.