Background The knowledge about what predicts progress of syndesmophytes that characterize patients with ankylosing spondylitis (AS) is limited. The strongest known predictor for radiographic progression in the spine is existing syndesmophytes at baseline.
Objectives To study the radiographic progression in the spine in AS patients in total and by gender and search for predictors for the changes.
Methods 204 patients with AS, all meeting the New York criteria, from three rheumatology departments in western Sweden were included in a longitudinal study. At baseline and after five years lateral radiographs of the cervical and lumbar spine were obtained and graded according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). All radiographs were assessed by the same experienced radiologist (MG). Predictors were assessed through questionnaires, back mobility tests and blood samples.
Results Of the 204 patients included at baseline, 169 (83%) patients were re-examined at the five year follow-up, 92 (54%) men and 77 (46%) women. At baseline, the median age (IQR) of the 169 patients was 49 (40 to 61.5) years old and the median duration of symptoms (IQR) was 22 (12 to 34) years, no significant difference in age or duration of symptoms between gender. Baseline mean mSASSS was 14.9±20.0 with progression to 16.4±20.8 at follow-up, an increase with 1.5±3.0 units (p<0.001). In men, mean baseline mSASSS was 22.0±23.5 and at follow-up 23.8±23.8, an increase of 1.8±2.8 units (p<0.001). In women, mean baseline mSASSS was 6.4±9.6 and 7.6±11.7 at follow-up, an increase of 1.2±3.3 (p=0.002). The mSASSS score at both baseline and at follow-up differed significantly between gender (p<0.001), whereas the progression of mSASSS did not differ significantly (p=0.2) between the groups. The presence of syndesmophytes at baseline was 47% in the whole group, 59.0% for men and 32.5% for women (p-value difference gender <0.001). In the total group 18.9% had had significant progression (≥4 mSASSS units over five years), 23.9% of the men and 13.0% of the women (p=0.11). Such rapid progression of mSASSS was in age-adjusted logistic regression models significantly predicted by baseline syndesmophyte and mean CRP during follow-up in men and baseline BASMI in women (table).
Conclusions The progression rate was 1.5±3.0 mSASSS units over five years and did not differ significantly between men and women, although being much higher in men at baseline in this cohort of AS patients with longstanding disease. Presence of existing syndesmophytes and persistent elevated CRP during follow-up were significant predictors for a change in ≥4 mSASSS units over five years in men whereas in women instead high BASMI was a significant predictor.
Disclosure of Interest None declared
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