Health state utility values (QALY weights) for Huntington's disease: an analysis of data from the European Huntington's Disease Network (EHDN)

Abstract

Background: Huntington's Disease (HD) is a hereditary neurodegenerative disorder which affects individuals' ability to walk, talk, think, and reason. Onset is usually in the forties, there are no therapies currently available that alter disease course, and life expectancy is 10-20 years from diagnosis. The gene causing HD is fully penetrant, with a 50% probability of passing the disease to offspring. Although the impacts of HD are substantial, there has been little report of the quality of life of people with the condition in a manner that can be used in economic evaluations of treatments for HD. Health state utility values (HSUVs), used to calculate quality-adjusted life-years (QALYs), are the metric commonly used to inform such healthcare policy decision-making.

Objectives: The aim was to report HSUVs for HD, with specific objectives to use European data to: (i) describe HSUVs by demographic and clinical characteristics; (ii) compare HSUVs of people with HD in the UK with population norms; (iii) identify the relative strength of demographic and clinical characteristics in predicting HSUVs.

Methods: European Huntington's Disease Network REGISTRY study data were used for analysis. This is a multi-centre, multi-national, observational, longitudinal study, which collects six-monthly demographic, clinical, and patient-reported outcome measures, including the SF-36. SF-36 scores were converted to SF-6D HSUVs and described by demographic and clinical characteristics. HSUVs from people with HD in the UK were compared with population norms. Regression analysis was used to estimate the relative strength of age, gender, time since diagnosis, and disease severity (according to the Total Function Capacity (TFC) score, and the UHDRS's Motor score, Behavioural score, and Cognition score) in predicting HSUVs.

Results: 11,328 questionnaires were completed by 5560 respondents with HD in 12 European countries. Women generally had lower HSUVs than men, and HSUVs were consistently lower than population norms for those with HD in the UK, and dropped with increasing disease severity. The regression model significantly accounted for the variance in SF-6D scores (n = 1939; F [7,1931] = 120.05; p < 0.001; adjusted R-squared 0.3007), with TFC score, Behavioural score, and male gender significant predictors of SF-6D values (p < 0.001).

Conclusion: To our knowledge, this is the first report of HSUVs for HD for countries other than the UK, and the first report of SF-6D HSUVs described for 12 European countries, according to demographic and clinical factors. Our analyses provide new insights into the relationships between HD disease characteristics and assessment of health-related quality of life in a form that can be used in policy-relevant economic evaluations.

Keywords: Cost-effectiveness analysis; Health state utility values; Huntington’s disease; Quality-adjusted life-years.

Fig. 1

Mean SF-6D health state utility values by age group

Fig. 2

Mean SF-6D health state utility values by disease stage