Utility Values for the CP-6D, a Cerebral Palsy-Specific Multi-Attribute Utility Instrument, Using a Discrete Choice Experiment

Background and Objective The CP-6D is a new preference-based measure derived from the CPQOL, a cerebral palsy-specific quality-of-life questionnaire. The CP-6D contains six dimensions, each with five levels. A preference-based value set is required to score the CP-6D on a utility scale and render it suitable for cost-utility analysis. This study aims to estimate the utility value set for the CP-6D for interventions for people with cerebral palsy (CP). Methods A discrete choice experiment was designed and administrated to an adult Australian online panel. Each respondent answered 12 choice sets. Each choice was presented as a combination of the health state from the CP-6D and duration spent in that health state before death. Conditional logit and mixed logit regression were used to analyse the data. The utility values were estimated as a ratio of the coefficient of each dimension to the coefficient of the duration. Results A total of 2002 participants completed the survey and responded to each choice. Generally, the dimension levels were monotonic, meaning the coefficients reflected the ordered nature of the levels in each dimension. The dimensions relating to manual ability, social well-being and acceptance had the greatest effect on choice. The value of the worst 'pits' health state is - 0.582. Conclusion This study provides the first CP-specific utility value set that can potentially be used in cost-utility analyses of interventions for people with CP where the CPQOL has been applied, both prospectively and retrospectively.