THE INFANTILE-ONSET GM2 CLINICAL RATING SCALE: FEASIBILITY, RELIABILITY, AND CONTRUCT VALIDITY OF REMOTE HEALTH-RELATED FUNCTION ASSESSMENT

GM2 gangliosidoses (Tay-Sachs/Sandhoff Diseases) are rapidly progressive genetic conditions characterized by developmental delay and decline in motor, cognitive, and language domains. To address the urgent needs of rare disease clinical trials, the Infantile-Onset GM2 Clinical Rating Scale (Infantile GM2-Scale) was developed based on caregiver reports of the meaningful impacts of GM2 on health-related function. An interdisciplinary team of PTs, OTs, and SLPs with expertise in infant function further refined the scale in focus groups. The scale was designed for both in-person and remote administration via videoconference. The purpose of this presentation is to report the feasibility, reliability, and initial evidence of construct validity for the Infantile GM2-Scale. Five infants with GM2 (mean age=25 months, range 14-46) completed remote visits every 45-90 days as part of a longitudinal natural history pilot study. The 16-item scale assesses 5 domains: Vision, Hand and arm use, Communication, Gross motor, and Feeding. Visits were conducted via Zoom and video recorded. Two trained pediatric physical therapists experienced in in-person and remote assessment of low functioning infants used a detailed manual to coach caregivers in facilitating item administration. Using data from 15 remote visits, feasibility, inter-rater reliability, and construct validity were evaluated. The Infantile GM2-Scale has the potential to improve clinical assessment of infants with Infantile GM2 and may have adaptive relevance for other rare conditions. Physical therapists are critical to designing, selecting, administering, scoring, and interpreting assessments of motor function in children with rare neurogenetic conditions.