Eliciting health state utilities for Aromatic L-amino Acid Decarboxylase (AADC) deficiency: a UK vignette study

Assessment of health state utilities associated with adult and pediatric acid sphingomyelinase deficiency (ASMD)

INTRODUCTION

Acid sphingomyelinase deficiency (ASMD) type B is a rare genetic disorder leading to enlargement of the spleen and liver, pulmonary dysfunction, and other symptoms. Cost-utility analyses are often conducted to quantify the value of new treatments, and these analyses require health state utilities. Therefore, the purpose of this study was to estimate utilities associated with varying levels of severity of adult and pediatric ASMD type B.

METHODS

Seven adult and seven child health state vignettes describing ASMD were developed based on published literature, clinical trial results, and interviews with clinicians, patients with ASMD, and parents of children with ASMD. The health states were valued in time trade-off interviews with adult general population respondents in the UK.

RESULTS

Interviews were completed with 202 participants (50.0% female; mean age = 41.3 years). The health state representing ASMD without impairment had the highest mean utility for both the adult and child health states (0.92/0.94), and severe ASMD had the lowest mean utility (0.33/0.45). Every child health state had a significantly greater utility than the corresponding adult health state. Differences between adult/child paired states ranged from 0.02 to 0.13. Subgroup analyses explored the impact of parenting status on valuation of child health states.

DISCUSSION

Greater severity of ASMD was associated with lower mean utility. Results have implications for valuation of pediatric health states. The resulting utilities may be useful in cost-utility modeling estimating the value of treatment for ASMD.

Time trade-off study to establish utility decrements in individuals with a spinal cord injury who perform intermittent catheterisation

AIMS

To generate utility decrements for three attributes associated with catheterisation for individuals with a spinal cord injury (SCI): the process of catheterisation, the physical impact of urinary tract infections (UTIs) and worry associated with hospitalisation.

MATERIALS AND METHODS

Health state vignettes comprising various levels of the three attributes were developed. Two cohorts of respondents, corresponding to people with SCIs and a sample broadly representative of the UK population, were presented with nine vignettes (three vignettes for the mild, moderate and severe health states in addition to a random set of six vignettes). It was assumed no or a nominal decrement was associated with the mild health state. Utility decrements were derived from analysing the data obtained from the online time trade-off (TTO). A proportion of the SCI cohort (n = 57) also completed the EQ-5D-5L questionnaire.

RESULTS

Utility decrements were generated using statistical models for the general population (n = 358), the SCI population (n = 48) and the two populations combined (merged model, n = 406). Results from the two cohorts showed minimal differences. For the merged model, SCI status was not statistically significant. All interaction terms, excluding SCI and the severe level of the physical attribute, were not statistically significant. Compared to the mild level, the greatest utility decrement calculated was the severe level of the emotional (worry) attribute (0.09, p < 0.001) for the SCI population. A significant decrement of 0.02 (p <0.001) was calculated for the moderate level of the emotional attribute for all models. The mean utility score for those with SCI having completed the EQ-5D-5L was 0.371.

LIMITATIONS

Modest sample size of respondents from the SCI population (n = 48).

CONCLUSIONS

Worry associated with hospitalisation had the greatest impact on patients' health-related quality of life (HRQoL). The catheterisation process, such as the lubrication and repositioning of the catheter, also impacted on patients' HRQoL.

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

Purpose

Cost-effectiveness evaluations of interventions require health utility data. However, in medical conditions, such as aromatic L-amino acid decarboxylase (AADC) deficiency, this presents problems due to the rarity of the disease. The study aim therefore was to employ a discrete choice experiment (DCE) to generate health utilities for AADC deficiency.

Methods

A previous literature review, clinician and parent interviews had identified six key AADC deficiency attributes: mobility, muscle weakness, oculogyric crises (OCG), feeding ability, cognitive impairment and screaming. A representative sample of the French general population was recruited. Participants rated 5 health state vignettes describing AADC deficiency using time-trade-off (TTO) and standard gamble (SG). Additionally, participants rated the worst health state using the Health Utility Index version 3 (HUI3). Subsequently, participants completed DCE 11 choice sets. Indirect DCE part-worth utilities were converted to health utilities using the anchors from the TTO, SG and HUI3.

Results

The DCE was completed online by 1001 participants (50.9% female; mean age 45.7 years). Most participants (596, 59.5%) provided consistent responses to the repeated choice task. Five models were evaluated, and one preference reversal (“head control”/“sitting unaided”) was identified in all models. The rescaled utilities ranged from 0.3891 to 0.5577 (difference of 0.17 utilities) for TTO anchors corresponding to the worst (633233) and best (111111) health states. Health utilities ranged from 0.5534 to 0.7093 for the SG anchors. The disutility associated with a transition from “no problems walking” to “bedridden” was −0.0533, whereas disutility of moving from “constant screaming” relative to “no screaming” was −0.0248. The disutility associated with daily OCG was −0.0167. Disutilities for the other attributes were small although there were exceptions.

Conclusion

A DCE was used to derive health utilities for AADC deficiency. These health utilities will subsequently be used in an economic model evaluating an AADC deficiency intervention.