QALY weights for diabetic retinopathy--a comparison of health state valuations with HUI-3, EQ-5D, EQ-VAS, and TTO.

OBJECTIVE

To estimate quality-adjusted life-year weights for patients with diabetic retinopathy by using various methods and to investigate the empirical validity of the different measures.

METHODS

The study population comprised 152 patients with diabetes in Östergötland County, Sweden. Participants were interviewed by telephone by using the time trade-off (TTO) method and a visual analogue scale (EQ-VAS) (direct valuations) as well as the EuroQol five-dimensional questionnaire (EQ-5D) and the health utilities index mark 3 (HUI-3) (indirect valuations). The quality-adjusted life-year weights were adjusted for potential confounders by using analysis of covariance. The empirical validity of the measures was examined by testing their ability to detect hypothetical differences between severity levels of diabetic retinopathy and by investigating the correlation between the measures and the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25).

RESULTS

All measures detected significant differences in scores between patient groups classified according to visual impairment in the better eye (analysis of covariance, P < 0.05), but only HUI-3 and EQ-VAS detected significant differences between patient groups classified according to visual impairment or pathological progression in the worse eye. HUI-3 recorded a difference of 0.43 in values between normal vision and blindness in the better eye, which was more than twice the differences captured by the other measures (0.15-0.20). In addition, HUI-3 showed the highest correlation with NEI VFQ-25 (r = 0.54; P < 0.001).

CONCLUSIONS

In cost-utility analyses, the choice of quality-adjusted life-year measure may affect whether an intervention is considered cost-effective. Furthermore, if decisions are to be based on values from the general public, HUI-3 can be recommended for cost-utility analyses of interventions directed at diabetic retinopathy.