Prevalence of axial spondyloarthritis in United States rheumatology practices: Assessment of SpondyloArthritis International Society criteria versus rheumatology expert clinical diagnosis.

Objective: New classification criteria for axial spondyloarthritis (SpA) have been validated by the Assessment of SpondyloArthritis international Society (ASAS) working group. We applied these criteria to estimate prevalence of SpA in randomly selected, retrospectively reviewed medical records from representative US rheumatology practices.

Methods: Rheumatologists from 101 US practices identified at-risk patients, ages 18-44 years, with chronic back pain.