Validity of EuroQOL-5D, time trade-off, and standard gamble for age-related macular degeneration in the Singapore population.
OBJECTIVE
Utility values of age-related macular degeneration (AMD) in Asian patients are unknown. This study aims to assess utility values and construct validity of the EuroQOL-5D (EQ-5D), time trade-off (TTO), and standard gamble (SG) instruments in the Singapore multi-ethnic AMD population.


METHODS
Cross-sectional, two-centre, institution-based study. Visual acuity (VA), clinical AMD severity, and utility scores on the EQ-5D, TTO, and SG were obtained from 338 AMD patients. VA was analysed in terms of the better-seeing eye (BEVA), worse-seeing eye (WEVA), and weighted average of both eyes (WVA). We evaluated SG on the perfect health-death (SG(death)) and binocular perfect vision-binocular blindness (SG(blindness)) scales. Construct validity was determined by testing a priorihypotheses relating the EQ-5D, TTO, and SG utility scores to VA and clinical AMD severity.


RESULTS
The mean utilities on the EQ-5D, TTO, SG(death), and SG(blindness) were 0.89, 0.81, 0.86, and 0.90, respectively. EQ-5D scores correlated weakly with BEVA, WEVA, and WVA (Pearson's correlation coefficients -0.291, -0.247, and -0.305 respectively, P<0.001 for all). SG(death) and SG(blindness) demonstrated no correlation with BEVA, WEVA, or WVA (Pearson's correlation coefficients, range -0.06 to -0.125). TTO showed weak association only with WEVA and WVA (correlation coefficients -0.237, -0.228, P<0.0001), but not with BEVA (correlation coefficient -0.161). Clinical AMD severity correlated with EQ-5D and SG(death), but not with TTO and SG(blindness) (P=0.004, 0.002, 0.235, and 0.069, respectively).


CONCLUSIONS
AMD has a negative impact on utilities, although utility scores were high compared with Western cohorts. EQ-5D, TTO, and SG showed suboptimal construct validity, suggesting that health status utilities may not be sufficiently robust for cost-utility analyses in this population.
Department of Ophthalmology and Visual Sciences, Khoo Teck Puat Hospital, Singapore. aekg@eyecataractretina.com
K G
KG
Au Eong
E W
EW
Chan
N
N
Luo
S H
SH
Wong
N W H
NW
Tan
T H
TH
Lim
A M
AM
Wagle
D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006304:Health Status; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology / Q000523:psychology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012846:Singapore; D014792:Visual Acuity / Q000502:physiology