There has been an increasing interest in developing country-specific preference weights for widely used measures of health-related quality of life. The valuation of health states has usually been done using cardinal preference elicitation techniques of standard gamble (SG) or time trade-off (TTO). Yet there is increasing interest in the use of ordinal methods to elicit health state utility values as an alternative to the more conventional cardinal techniques. This raises the issue of firstly whether ordinal and cardinal methods of preference elicitation provide similar results and secondly whether this relationship is robust across different valuation studies and different populations.
This study examines SG and rank preference weights for the SF-6D derived from samples of the UK and Portuguese general population. The preference weights for the Portuguese sample (n = 140) using rank data are estimated here with 810 health state valuations. The study further examines whether the use of these different preference weights has an impact when comparing the health of different age and severity groups in the Portuguese working population (n = 2,459).
The rank model performed well across the majority of measures of goodness of fit used. The preference weights for the Portuguese sample using rank data are systematically lower than the UK weights for physical functioning and pain. Yet our results suggest higher similarity between preference weights derived using rank data than using standard gamble across the UK and Portuguese samples. Our results further suggest that the SF-6D values for a sample of the Portuguese working-age population and differences across groups are affected by the use of different preference weights.
We suggest that the use of a Portuguese SF-6D weighting system is preferred for studies aiming to reflect the health state preferences of the Portuguese population.