Association Between Myasthenia Gravis–Activities of Daily Living (MG-ADL) and EQ-5D-5L Utility Values: The Additional Effect of Efgartigimod on Utilities

INTRODUCTION: For patients with generalized myasthenia gravis (gMG), the association between symptom severity, often measured with the Myasthenia Gravis Activities of Daily Living (MG-ADL) instrument, and utility values is unknown. METHODS: Data was analyzed from the phase 3 ADAPT trial, which included adult patients with gMG randomly assigned to treatment with efgartigimod + conventional therapy (EFG + CT) or placebo + CT (PBO + CT). MG-ADL total symptom scores and the EQ-5D-5L, a measure of health-related quality of life (HRQoL), were collected biweekly up to 26 weeks. Utility values were derived from the EQ-5D-5L data with the United Kingdom value set. Descriptive statistics were reported for MG-ADL and EQ-5D-5L at baseline and follow-up. A normal identity-link regression model estimated the association between utility and the eight MG-ADL items. A generalized estimating equations (GEE) model was estimated to predict utility based on the patient’s MG-ADL score and treatment received. RESULTS: A total of 167 patients (84 EFG + CT, 83 PBO + CT) contributed 167 baseline and 2867 follow-up measurements of MG-ADL and EQ-5D-5L. EFG + CT-treated patients experienced more improvements than PBO + CT-treated patients in most MG-ADL items and EQ-5D-5L dimensions, with the largest improvements observed in chewing, brushing teeth/combing hair, eyelid droop (MG-ADL); self-care, usual activities, mobility (EQ-5D-5L). The regression model indicated that individual MG-ADL items contributed differently to utility values, with the largest impact from brushing teeth/combing hair, rising from a chair, chewing, and breathing. The GEE model showed that each unit improvement in MG-ADL led to a statistically significant utility increase of 0.0233 (p < 0.001). In addition, a statistically significant improvement of 0.0598 (p = 0.0079) in utility was found for patients in the EFG + CT group compared to the PBO + CT group. CONCLUSION: Among patients with gMG, improvements in MG-ADL were significantly associated with higher utility values. MG-ADL scores alone were not sufficient to capture the utility gained from efgartigimod therapy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12325-023-02437-w.