Estimating an exchange-rate between care-related and health-related quality of life outcomes for economic evaluation: An application of the wellbeing valuation method

Background: Quality of life outcomes for family carers and patients may be measured in different ways within the same economic evaluation. Methods: We used the wellbeing valuation method to calculate "exchange rates" between care-related outcomes (the Carer Experience Scale and CarerQoL-7D) and health-related (the EQ-5D-5L) outcomes. Data on quality of life outcomes were collected through a postal quality of life survey in the UK. A random effects model was used to estimate carers' wellbeing as a function of their EQ-5D-5L, Carer Experience Scale (or CarerQoL-7D) and a set of control variables. Results: When life satisfaction was used as the measure of wellbeing, a one-point gain in the Carer Experience Scale (0-100 scale) was equivalent (in wellbeing terms) to a 0.014 gain in EQ-5D-5L value; and a one point gain in the CarerQoL-7D (0-100 scale) was equivalent to a 0.033 gain in EQ-5D-5L. The exchange rate values were reduced when capability was used as the measure of wellbeing. Conclusions: The exchange rates estimated in this study offer a means to place carer and patient outcomes, measured via different quality of life instruments, on a common scale, although there are important issues to consider in operationalising the technique.