Background Enthesitis-related arthritis (ERA) is the third most common category of juvenile idiopathic arthritis (JIA), encompassing 10-15% of JIA cases. ERA includes certain forms of spondyloarthritis, which differ from other JIA subtypes regarding clinical phenotype, genetic background, and disease course. Meanwhile, newly developed assessment tools are available, allowing for a better and more comparable assessment of the outcome of ERA.
Objectives To examine disease features and activity in patients with ERA during the first 12 months of paediatric rheumatology care, and to assess the validity of a modified version of the Juvenile Spondylarthritis Disease Activity Index (mJSpADA).
Methods We analysed data of patients with ERA included in the Inception Cohort of Newly diagnosed patients with juvenile idiopathic arthritis (ICON). Disease features (e.g., arthritis, enthesitis, uveitis), disease activity (JIA core set criteria, JADAS, mJSpADA), patient's functional status (CHAQ), and quality of life (by PedsQL) were assessed quarterly during the first 12 months in ICON. Changes in disease parameters from baseline to the 12-month-follow-up were analysed by paired t-tests. Spearman's correlation coefficient was used to evaluate the relationship between mJSpADA and other measures of disease activity. Responsiveness to change in disease activity over time was tested by comparing the change in the mJSpADA score between visits in patients who had a Ped-ACR-30 response. Discriminant validity was evaluated by comparing the mean JSpADA scores with physician global assessment (0 or >0) and determining the area under curve at the 12-month-follow-up.
Results The analysis considered 58 patients (76% male) with a mean age of 11.8 years and a mean disease duration of 8.7 months at inclusion. ERA was diagnosed on average 3.4 months before the baseline visit. At first assessment, patients had 3.3 active joints (mean) and 3.2 joints with LOM. JADAS-10 was 10.3 (mean), JADAS-71 10.9. The mean pain level was 3.4, the median CHAQ score 0.45, the median PedsQL-score 70.9. During the first year of specialised care, 95% of patients received NSAIDs, 55% MTX and 27% biologics. At the 12-month-follow-up, 41.4% of patients had an inactive disease, 49% had no functional limitations. The mJSpADA score was significantly lower compared to baseline (mean 0.9 vs. 2.1). At follow-up, the mJSpADA had high or moderate correlations with the JADAS-10 (r=0.82), the physician's (r=0.63) and patient's global assessment (r=0.62), and was negatively correlated with the PedsQL (r=-0.37). The mJSpADA was responsive to improvement (Ped-ACR-30 response, OR =0.47, 95%CI: 0.26 – 0.86, AUC=0.72) and discriminated between active and inactive disease (AUC=0.84).
Conclusions Current routine care significantly reduces disease activity in patients with early ERA. About 40% achieve an inactive disease state within one year of specialised care. The mJSpADA seems to be a useful tool to measure disease activity in ERA patients over time.
Acknowledgements ICON is funded by the Federal Ministry of Research (FKZ: 01ER0812)
Disclosure of Interest M. Niewerth: None declared, J. Klotsche: None declared, I. Liedmann: None declared, A. Hospach: None declared, G. Horneff Grant/research support from: Pfizer, Abbvie, Roche/Chugai, Consultant for: Pfizer, Chugai, A. Thon: None declared, H.-I. Huppertz: None declared, J. Kümmerle-Deschner: None declared, C. Sengler: None declared, K. Minden Grant/research support from: Pfizer, Abbvie, Consultant for: Pfizer, Chugai