Spinal radiographic changes in ankylosing spondylitis: association with clinical characteristics and functional outcome.

OBJECTIVE: To determine which patients with ankylosing spondylitis (AS) have radiographic spinal damage and to investigate the relation between radiographic spinal changes and limitations in physical function.
METHODS: A cross-sectional nationwide study in Belgium of patients with AS under the care of a rheumatologist. The treating physician completed a questionnaire including clinical disease manifestations and laboratory findings (HLA-B27 and C-reactive protein), and classified spinal radiographs into 3 categories: (1) no AS-related spinal abnormalities; (2) syndesmophytes; and (3) spinal ankylosis. Patients completed the Bath AS Disease Activity Index (BASDAI) and the Bath AS Functional Index (BASFI). Ordinal regressions were performed to quantify the relationship between clinical manifestations and spinal radiographic changes. Generalized linear models were computed to quantify relationships among clinical manifestations, radiographic spinal changes, and functioning (BASFI).
RESULTS: A total of 619 patients fulfilled modified New York criteria for definite AS and had evaluable radiographic data; 68% were male and disease duration was 17.5 (SD 12.2) years. Male sex, younger age at symptom onset, and hip involvement were associated with radiographic changes; but HLA-B27, peripheral arthritis, and extraarticular disease status (uveitis, psoriasis, and inflammatory bowel disease) were not. Older age, BASDAI, hip involvement, and spinal change contributed to BASFI; but sex, disease duration, peripheral arthritis, and extraarticular manifestations did not.
CONCLUSION: Radiographic spinal changes in patients with AS are seen more often in men and those with hip involvement. BASFI status indicates the influence of radiographic changes and hip involvement, but does not reflect the presence of peripheral arthritis and does not differ between men and women.