Juvenile Spondyloarthritis Disease Activity Index Validation in Enthesitis-Related Arthritis and Juvenile Psoriatic Arthritis in a Prospective Clinical Trial Setting.

OBJECTIVE To investigate the validity of the Juvenile Spondyloarthritis Disease Activity Index (JSpADA) in children with enthesitis-related arthritis (ERA) or juvenile psoriatic arthritis (jPsA) in a prospective clinical trial setting. METHODS JUNIPERA (NCT03031782) is a phase 3, placebo-controlled withdrawal study investigating the safety and efficacy of secukinumab in children with ERA and jPsA. After 12 weeks of open-label treatment with secukinumab, patients were randomized 1:1 to secukinumab or placebo until disease flare or Week 52. JSpADA validity was assessed using 3 criteria: convergent validity (Spearman's correlation) at Week 12 with the Juvenile Arthritis Disease Activity Score in 10 joints (JADAS-10), clinical JADAS-10 (cJADAS-10), and physician global assessment of disease activity (PGA); discriminatory validity at Week 12 among patients with active or inactive disease and JIA ACR response criteria; and responsiveness to change in clinical disease activity from Weeks 12 to 52. RESULTS At Week 12, mean (SD) JSpADA scores showed moderate-to-good correlation with JADAS-10, cJADAS-10, and PGA scores (all Spearman ρ > 0.4) and were higher among patients with active vs inactive disease (1.8 [1.3] vs 0.5 [0.8], P < 0.001). Patients with improved disease activity from Weeks 12 to 52 had greater improvements in JSpADA than patients with worsening disease (-0.8 [1.1] vs 0.4 [1.0], P < 0.001); patients with stable disease had minimal change in JSpADA (-0.1 [0.5]). Validity results were similar for ERA and jPsA. CONCLUSION These results validate JSpADA as a disease activity measure for children with ERA and jPsA in a prospective clinical trial setting.