Abstract
PurposeThe aim of this study was to generate health state utilities for aromatic L-amino acid decarboxylase (AADC) deficiency, a rare genetic, lifelong neurogenerative condition predominantly manifesting in young infants.MethodsParticipants were presented with health state vignettes. These had been previously developed based on published literature, clinician input, interviews with parents of AADC deficiency patients and expert opinion. A total of 5 health state vignettes were presented: bedridden, head control, sitting unsupported, standing with assistance and walking with assistance. Health state utilities (HSU) were elicited using time-trade off (TTO; 10-year time horizon) and the standard gamble (SG). The vignettes were completed online by panel participants drawn from a representative sample of the United Kingdom residential population.ResultsA total of 1598 participants completed the vignettes. Around 21% had incongruent responses (higher utilities for the bedridden compared to walking health states). Incongruent responses were associated with shorter task completion times, gender and parental status. These responses were removed from the analysis. Health state utilities (HSU) increased correspondingly as health states improved for both the TTO and SG. The mean HSU (standard deviation) for the TTO task were: bedridden state 0.49 (0.34); head control 0.54 (0.33), sitting unsupported 0.63 (0.31); standing with assistance 0.68 (0.31); and walking with assistance 0.73 (0.31). For the SG, mean health state utilities were: 0.56 (0.28), 0.57 (0.27), 0.67 (0.24), 0.70 (0.24), and 0.75 (0.25), respectively.ConclusionHealth state utilities were derived for AADC deficiency through a vignette study. These will be used for a cost-effectiveness model of an AADC deficiency treatment.
Highlights
Aromatic L-amino decarboxylase (AADC) deficiency is a genetic condition, which typically presents in early infancy
The results indicated not being a parent (B = − 0.41, standard error (SE) = 0.14, p = 0.003, odds ratio (OR) = 0.67 (95%confidence intervals (CIs) 0.51 to 0.87)) and being female (B = − 0.32, SE = 0.13, p = 0.013, OR = 0.73 (95%CI 0.56 to 0.94)) is less likely to be associated with incongruent responses
In conclusion, health state utilities were derived for AADC deficiency from a large sample size with incongruent responses removed and a high degree of logical consistency in the utility ordering of the health states
Summary
Aromatic L-amino decarboxylase (AADC) deficiency is a genetic condition, which typically presents in early infancy. It is a rare condition with only around 150 reported cases worldwide [1, 2]. Patients with the severe phenotype will be bedridden for life [2], will not achieve developmental milestones and will be fully dependent for care. Even cases with the mild phenotype will display a degree of developmental delay, cognitive disability and require assistance with walking. AADC deficiency clearly has the potential to significantly impact on patients’ health-related quality of life (HRQoL), the nature and rarity of AADC deficiency means it is difficult to derive robust health state utilities from either the child or their parent/caregiver [4, 5]. Are HRQoL assessments necessary to evaluate the impact
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