Modified Juvenile Spondyloarthritis Disease Activity Index in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry

Objective To validate the Juvenile Spondyloarthritis Disease Activity Index (JSpADA), and modified versions thereof, in a North American cohort of patients with enthesitis-related arthritis (ERA).

Methods We utilized the Childhood Arthritis and Rheumatology Research Alliance Registry database ERA cohort to validate the JSpADA and its modifications (JSpADA6-no Schober, no C-reactive protein [CRP]/erythrocyte sedimentation rate [ESR]; JSpADA7-no Schober; and JSpADA7-no CRP/ESR) using the Outcome Measures in Rheumatology principles of face validity, discriminative validity, and responsiveness to change.

Results There were 51 subjects (64 visits) with complete JSpADA data with a mean age of 13.7 years and disease duration of 30.9 months. Subjects were predominantly White (84.3%), and 56.9% were male and 50% were HLA-B27 positive. The JSpADA showed high correlation with the clinical 10-joint Juvenile Arthritis Disease Activity Score (cJADAS10; r = 0.81), moderate-to-high correlation with physician global assessment (PGA; r = 0.69), and low-to-fair correlation with Childhood Health Assessment Questionnaire (CHAQ; r = 0.22). The modifications of the JSpADA (JSpADA7-no Schober; JSpADA7-no CRP/ESR; and JSpADA6-no Schober, no CRP/ESR) performed similarly with high correlation with cJADAS10 (r = 0.81, 0.79, and 0.80, respectively), moderate-to-high correlation with PGA (r = 0.65, 0.67, 0.64, respectively), and low-to-fair correlation with CHAQ (r = 0.35, 0.34, 0.39, respectively). All modified versions of JSpADA had good responsiveness to change. All versions of JSpADA had excellent discriminative validity.

Conclusion We propose the term modified JSpADA for the modification of JSpADA with 6 elements (JSpADA6-no Schober, no CRP/ESR). This shorter disease activity index may improve implementation of JSpADA in both clinical practice and research trials.