Performances of the Assessment of SpondyloArthritis International Society axial spondyloarthritis criteria for diagnostic and classification purposes in patients visiting a rheumatologist because of chronic back pain: results from a multicenter, cross-sectional study.

OBJECTIVE: To evaluate the performances (sensitivity, specificity, and positive and negative predictive values) at diagnosis and study visit of the Assessment of SpondyloArthritis international Society (ASAS) criteria in axial spondyloarthritis in patients with chronic back pain (CBP). A secondary objective was to identify the most contributory item to diagnosis/classify spondyloarthritis. METHODS: We conducted a multicenter, cross-sectional study. Patients were ages <45 years with a history of CBP and seeing a rheumatologist in France. Data included items from the different sets of criteria, checking if present at diagnosis ("diagnosis")/after diagnosis, but at study visit ("classification"), and the rheumatologist's diagnosis at study visit. Statistical analysis included descriptive characteristics and performances for diagnosis and classification. The diagnosis of the rheumatologist was considered the "gold standard." RESULTS: A total of 1,210 patients were eligible for our analysis. Sensitivity and specificity for ASAS axial criteria were 0.76 and 0.94, respectively, and 0.87 and 0.92 for diagnostic and classification purposes, respectively. The positive likelihood ratio of the ASAS axial criteria was 13.6 and 10.30 for diagnostic and classification purposes, respectively. The most contributory items to diagnosis and classification were radiographic sacroiliitis, followed by magnetic resonance imaging sacroiliitis for diagnosis and history of uveitis for classification. CONCLUSION: We confirm the validity of the ASAS criteria for both diagnostic and classification purposes in a clinical setting of patients with CBP.