Estimation of Health Utility Scores for Glycogen Storage Disease Type Ia.

Abstract

Glycogen Storage Disease Type Ia (GSDIa) is a rare genetic metabolic disorder characterized by hypoglycemia, hepatomegaly, growth failure, and possible seizures/death. Patients frequently consume cornstarch to maintain blood glucose. Evidence demonstrating the impact of GSDIa on health-related quality of life (HRQoL) is lacking. This study aims to understand the burden of GSDIa by obtaining utility values for economic appraisals. A targeted literature review and interviews with experts (n=4) and caregivers (n=4) informed the development of health state vignettes describing different GSDIa severities by age and level of hypothetical treatment (i.e., gene therapy) response. Health states reflecting caregivers' experiences were also developed. A convenience sample of the UK general public completed a time trade-off (TTO) exercise. Scores conceptually varied from 0 (dead) to 1 (full health). States were also rated using a visual analog scale (VAS) and the EQ-5D-5L. Data were descriptively summarized. One hundred participants completed the exercise (male: 48%; mean age: 42 years). Scores were lowest for the adolescent pre-treatment state (TTO=0.38). Large increments in HRQoL were observed for the response (adult: TTO=0.86; child: TTO=0.84) and complete response (adult and child: TTO=0.94) hypothetical treatment response states. Caregiver values were lowest for the pre-treatment state (TTO=0.57) and highest for the complete response state (TTO=0.95). VAS and EQ-5D-5L scores followed a similar pattern. This study found an HRQoL burden on GSDIa patients and caregivers, with potential large improvement from a hypothetical treatment. These findings may be useful for families, clinicians, regulatory agencies, and in therapy economic evaluations.