DESIR is a prospective longitudinal multicentric French cohort of patients with inflammatory back pain suggestive of spondyloarthritis, with a 10-year-follow-up. The purpose is to evaluate the performances of the different sets of classification criteria for axial spondyloarthritis, and to describe the frequency and characteristics of the clinical features of axial spondyloarthritis.

Demographic data and items allowing classification and indices calculation were collected, as well as biologic and imaging data. Baseline data are analyzed. The performance of the several classification criteria sets was evaluated (likelihood ratio) with the physician's diagnosis as external gold standard. For the clinical presentation of axial spondyloarthritis, a descriptive analysis was conducted.

Seven hundred and eight patients are included. Ninety-two percent of them satisfy at least one set of classification criteria: mNY 26%, Amor 79%, ESSG 78%, ASAS 70%; physician's confidence level 6.8±2.7. 81 and 83% of patients fulfil modified (including MRI) Amor or ESSG criteria. Axial involvement is present in 100% of the cases. NSAIDs are taken by 90%, with an NSAID sore of 50±46. BASDAI over 40 is noted in 60% and elevated CRP in 30% of the cases. HLA-B27 is present in 58%. According to ASDAS CRP levels, 12.7% are in inactive disease, 63% in high disease activity; mean BASFI was 30. Peripheral involvement is present in 57%, with arthritis in 37% of these. Enthesitis is noted in 49% of the patients, and first symptom in 22.5%; anterior chest wall involvement is noted in 44.6%, and dactylitis in 13%. For extra articular manifestations, psoriasis is recorded in 16%, uveitis in 8.5% and IBD in 5.1%. Smoking is present in 36.3% and hypertension in 5.1% of the cases.

These data represent the base of evaluation of the follow-up of this cohort, allowing future specific studies.