Development and initial validation of parent and child versions of the Juvenile Arthritis Disease Activity Score

Objective To develop parent- and child-centred versions of the Juvenile Arthritis Disease Activity Score (JADAS) and to provide preliminary evidence of their validity. Methods Validation analyses were conducted on two large multinational datasets of patients with juvenile idiopathic arthritis (JIA) and included assessment of construct validity, internal consistency and structure, discriminative validity, responsiveness to change, and predictive validity. Results The parJADAS and patJADAS include four parent/patient-reported outcomes, each measured on a 0-10 scale: assessment of overall disease activity; rating of pain intensity; assessment of activity of joint disease; and duration of morning stiffness. Both scores are calculated as the simple linear sum of the scores of their four components, which yield for both of them a global score of 0-40. The parJADAS and patJADAS demonstrated good construct validity, yielding high correlations with other JIA composite disease activity measures and moderate correlations with physician global rating and joint counts. Internal consistency was satisfactory, with Cronbach's alpha > 0.80, and exploratory factor analysis showed that both indices are monodimensional. Both instruments discriminated well between different disease states, with discriminative ability being unaffected by the presence of damage; proved able to predict important disease outcomes; and showed fair responsiveness to clinically important change, with standardized response mean of 0.71. Conclusion Both parJADAS and patJADAS were found to possess good measurement properties and to serve as a surrogate of physicians' evaluations. Regular home completion of the two instruments through digital technologies offers a suitable and pragmatic approach to deliver remote symptom monitoring and telehealth.