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Thomas Butt, Hannah Dunbar, Steve Morris, Shepley Orr, Gary Rubin; Comparing Patient and Public Preferences for Health States Associated with Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4419.
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Health utility values suitable for calculating quality-adjusted life years (QALYs) are increasingly used to assess the cost effectiveness of treatments for age-related macular degeneration (AMD). Health care decision makers disagree whether to use members of the public or patients to provide utilities. The public offer an unbiased view of health states, unaffected by the condition they are valuing, whereas patients are likely to have a greater understanding of the condition and its effects on quality of life. Our aim was to test if utility values for health states associated with AMD elicited directly from patients were different from those calculated from public tariffs for health-related quality of life (HRQoL) questionnaires.
Generic preference-based HRQoL questionnaires (EQ-5D and SF-6D) and the time trade-off (TTO) and visual analogue scale (VAS) valuation techniques were administered to a sample of UK patients with AMD (N=60, visual acuities: 0.3 to 1.3 logMAR). Health utilities were calculated using standard general population tariffs for the patient EQ-5D and SF-6D health states and directly from patient TTO and VAS scores.
Mean utilities derived from the public tariffs were 0.613 (SD=0.275) for the EQ-5D and 0.628 (SD=0.114) for the SF-6D. Mean utilities elicited from patients were 0.481 (SD=0.411) for the TTO and 0.567 (SD=0.218) for the VAS. Repeated measures analysis of variance (ANOVA) identified a significant difference between the four utility measures (p<0.01). Paired t-tests found no significant difference between the two public-derived utilities (EQ-5D and SF6D). Differences between the EQ-5D and patient-derived utilities (TTO and VAS) were both significant (p<0.05). Visual acuity (VA) in the better-seeing eye was not associated with any utility measure. The VAS was the measure best predicted by VA: R-squared=0.06, p>0.2.
Patient and public preferences for health states associated with AMD are different, with patients valuing their health state more severely than the public tariffs of commonly used HRQoL questionnaires. VA did not predict health utility using any measure and therefore care should be taken when using VA as a surrogate measure for utility in health economic analyses.
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