Evaluating anchor variables and variation in meaningful score differences for PROMIS® Pediatric measures in children and adolescents living with a rheumatic disease

Purpose Meaningful score differences (MSDs), as defined by recent FDA guidance, can improve the interpretation of outcome measure scores and score changes. Well-accepted methods for estimating MSDs typically rely on external anchor variables, but the applications of these methods are limited in children and adolescents with rheumatic diseases. This project explored multiple candidate anchors for the PROMIS ® Pediatric measures of Physical Activity, Fatigue, Pain Interference, and Mobility for children with juvenile idiopathic arthritis (JIA) or systemic lupus erythematosus (SLE). Methods Longitudinal data were extracted from the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry. Candidate anchors included patient-reported domain-specific global impressions of change (GIC) along with other parent- and clinician-reported variables. Prior to MSD estimation, the quality of the anchors was assessed using a priori criteria (correlation ≥0.30, n≥10,