Overall characteristics of the referred patients
| Age (years), mean±SD | Age of back pain onset (years), mean±SD | Duration of back pain (years), mean±SD | Males (%) | HLA-B27+ (%) | |
|---|---|---|---|---|---|
| All patients (n=522) | 41.4±13.0 | 32.4±11.4 | 9.0±9.3 | 48.1 | 62.3 |
| All axial SpA patients (n=228) | 37.2±11.7 | 29.3±9.1 | 8.0±8.8 | 55.3 | 86.0 |
| AS (n=119) | 39.6±12.9 | 29.3±9.2 | 10.3±10.0 | 58.0 | 87.4 |
| Nr-axSpA (n=109) | 34.6±9.6 | 29.3±8.9 | 5.4±6.7 | 52.3 | 84.4 |
| Possible SpA (n=38) | 36.4±10.3 | 29.8±8.7 | 6.6±5.6 | 44.7 | 57.9 |
| Non-SpA (n=256) | 45.8±13.0 | 35.6±12.7 | 10.2±9.9 | 42.2 | 41.8 |
AS, ankylosing spondylitis; nr-axSpA, non-radiographic axial spondyloarthritis; SpA, spondyloarthritis.