A comparison of injured patient and general population valuations of EQ-5D health states for New Zealand

BACKGROUND A near-universal finding internationally is that patient valuations of their own health, represented using the EQ-5D system, are mostly higher than general population valuations of the same EQ-5D states. This paper investigates whether this result also applies to New Zealand. Despite the EQ-5D's widespread use for cost-utility analysis in New Zealand, in particular by the Pharmaceutical Management Agency (PHARMAC) for health technology assessments, no previous studies comparing patient and general population valuations have included data for New Zealand. METHODS Valuations of 13 EQ-5D health states from a 1999 survey of the New Zealand general population (n = 396) are compared with injured New Zealanders' (n = 2099) valuations of their own health (also represented on the EQ-5D) collected between 2007 and 2009 in the Prospective Outcomes of Injury Study. Which EQ-5D dimensions are most strongly associated with the population valuations is also investigated. RESULTS Injured population valuations are higher (better-rated health) than general population valuations for all 13 health states considered except 11111 (no problems on any EQ-5D dimension). This difference, which tends to be larger the 'worse' the state, is statistically significant at the 10% level for most of the states. State 11111 is rated significantly lower by the injured population than the general population. Pain/discomfort is more important in determining valuations for the general population than for injured people, whereas problems with self-care are more important for the injured population; anxiety/depression is important in both general and injured population valuations. CONCLUSIONS Consistent with the international literature, injured people's valuations of their own health are mostly higher than the general population's hypothetical valuations of the same EQ-5D states for New Zealand. These differences are practically significant in the sense that they are larger than minimally important differences for the EQ-5D from the literature, and they appear capable of significantly affecting CUA results.