Background The most unique feature in ankylosing spondylitis (AS) is subchondral eburnation and syndesmophytes, possibly leading to ankylosis and spinal fusion. So far a few comparisons of spinal bone formation between adult onset AS (AoAS) and Juvenile onset AS (JoAS) have been done. However, prospective studies of this comparison have not been accomplished.
Objectives The aim of this study was to evaluate difference of radiographic progression over 5 years between JoAS and AoAS.
Methods A total of 533 patients (115 patients with JoAS, 418 patients with AoAS) from the Observation Study of Korean spondyloArthropathy Registry (OSKAR) cohort were enrolled. We used a two-step approach to compare the radiographic progression between the JoAS and the AoAS. First, all OSKAR data were analyzed in relation to the onset of disease on cross-sectional survey. Second, we analyzed the radiographic spinal progression between groups over 5 years. The modified Stoke AS Spinal Score (mSASSS) were examined by two experienced radiologists to validate the results. The collection of the clinical parameters was conducted to investigate the associations between clinical factors and the radiographic progression. Univariable and multivariable regression analyses were done after adjusting for potential confounding factors, such as age, gender, disease duration, history of peripheral arthritis, baseline CRP level, baseline mSASSS, and NSAID intakes).
Results The agreement between the two readers regarding mSASSS was very good: ICC coefficient 0.75 (95% CI 0.61-0.82) and 0.71 (95% CI 0.58-0.82) at each time. On cross-sectional survey, in spite of adjusting for multiple comparisons by Bonferroni correction, the patients with JoAS had fewer mSASSS unit than those with AoAS (14.12±1.30 vs 18.58±0.85, p=0.005). In analysis over 5 years, the mean progression of mSASSS in patients with JoAS was 0.21±1.29 units, while that of mSASSS in patients with AoAS was 4.00±0.59 units (p=0.012).
Conclusions The patients with JoAS had slower radiographic spinal damage progression over 5 years than those with AoAS.
Disclosure of Interest None declared