PRO50 A Discrete Choice Experiment to Derive Health State Utilities for Aromatic L-Amino Acid Decarboxylase (AADC) Deficiency in France

Abstract

In the absence of utilities from clinical trials, deriving health utilities for ultra-rare medical conditions such as aromatic L-amino acid decarboxylase (AADC) deficiency poses challenges and requires alternative approaches, e.g. discrete choice experiments (DCE), in order to provide health utilities for cost-effectiveness evaluations of AADC interventions. The study aim was to generate health utilities using a DCE associated with AADC deficiency. The 6 key AADC deficiency attributes (2-6 levels), including mobility, muscle weakness, oculogyric crises (OCG), feeding ability, cognitive impairment and screaming had been identified from published literature, clinician input, parent interviews and expert opinion. Participants from a representative sample of the French general population were presented online with 10 choice sets, including one with reversed levels to evaluate choice consistency. Participants also rated 5 health state vignettes describing AADC deficiency. These were used to elicit utilities using time-trade-off. The utilities for the worst/best health states were used as anchors to convert indirect DCE part-worth utilities to health utilities. A total of 1001 participants completed the DCE (50.9% female, 49.1% male; mean age 45.7 years). Overall, five models were evaluated. Rescaled utilities using the health state utilities as anchors ranged from 0.3891 to 0.5577 (difference of 0.17 utilities), corresponding to the worst (633233) and best (111111) health states. The mean health states utilities were 0.389 for the bedridden state; head control 0.432, sitting unsupported 0.489; standing with assistance 0.526; and walking with assistance 0.558. The disutility moving from “walking with assistance” to “bedridden” was -0.0533; the disutility of “constant screaming” relative to “no screaming” was -0.0248; and, the disutility of daily OCG was -0.0167. Utilities for AADC deficiency were derived through a DCE to allow the usage in an economic model.