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

Abstract

BackgroundA 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.MethodsValuations 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.ResultsInjured 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.ConclusionsConsistent 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.

Psychological morbidity and health-related quality of life after injury: multicentre cohort study

“…Thirty per cent of eligible patients who were invited to join the study participated, and some selection bias may have occurred if those choosing to participate had higher or lower pre-injury HRQoL than those not participating. Follow-up rates were higher than or comparable to similar studies [16, 50, 52–55] but lower than opt-out registry-based cohort studies [56]. There was evidence of some response bias (online Table 2); in particular, young, single males were less likely to return follow-up questionnaires as were those reporting more problems with alcohol and drugs, higher pain scores, poorer social functioning and less social support.…”

“…Previous studies show retrospectively reported pre-injury HRQoL amongst injured populations is likely to show a small upward bias [38, 39, 52], for a variety of reasons [38, 39, 52, 57]. It is possible that some of the reduction in EQ-5D in our study arose from overestimation of pre-injury EQ-5D.…”

Subsequent Injury Study (SInS): Improving outcomes for injured New Zealanders

“…For many measures, participants were asked about their status before their sentinel injury, as well as at 3, 5, 12 and 24 months afterwards,13 allowing adjustment for pre-sentinel injury status. Validated outcome measures include WHO Disability Assessment Schedule (WHODAS; disability),47 Kessler-6 (psychological distress)48 and the EQ-5D (general health status)49 allowing the estimation of quality-adjusted life-years (QALYs; health states given an overall social preference value or ‘utility’) for ACC-SI 50 51

The ACC electronic database : Provides information about SI not available from the POIS interviews in isolation, including (1) date of ACC-SI event, (2) ACC-SI nature of injury grouping, (3) anatomical site, (4) diagnosis codes to derive ACC-SI severity, standard errors (5) mechanism and location of SI event, (6) whether ACC-SIs were entitlement or treatment-only claims, (7) whether ACC-SIs resulted in ACC earnings-related compensation payments (and dates) and (8) health and rehabilitation services provided and associated costs.

The NMDS : Provides information about ACC-SI resulting in hospitalisation (and hospital treatment exceeding 3 hours), including the length of stay, procedure codes and diagnoses at discharge.

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“…For many measures, participants were asked about their status before their sentinel injury, as well as at 3, 5, 12 and 24 months afterwards,13 allowing adjustment for pre-sentinel injury status. Validated outcome measures include WHO Disability Assessment Schedule (WHODAS; disability),47 Kessler-6 (psychological distress)48 and the EQ-5D (general health status)49 allowing the estimation of quality-adjusted life-years (QALYs; health states given an overall social preference value or ‘utility’) for ACC-SI 50 51…”

Psychological morbidity and return to work after injury: multicentre cohort study

“…Follow-up rates were higher than, or comparable with, those of studies that used similar recruitment methods. [38][39][40][41][42] Limitations include a potential selection bias: 30% of eligible patients who were approached took part, and participants and non-participants may have differed in terms of their likelihood of returning to work. It was also not possible to explore the impact of injuries on changes to jobs and hours of work; further work is required to address this.…”