Validity of the time trade-off and standard gamble methods of utility assessment in retinal patients.
OBJECTIVE
To assess the validity of the time trade-off (TTO) and standard reference gamble (SRG) techniques of utility assessment in patients with retinal disease. A cross section of eligible patients was studied and validity was determined through their relation with two logical constructs, visual acuity and scores from the Visual Function 14 (VF-14) index.


METHODS
The study consisted of eligible patients presenting to a tertiary retinal facility who completed an interview. All patients had best corrected vision of 20/40 or worse in at least one eye. TTO and SRG utilities, as well as a VF-14 questionnaire, were administered through a standardised interview. Demographic and clinical (including Snellen visual acuity) information was also collected.


RESULTS
323 patients met these study criteria. Significant predictors of TTO utilities in the multivariate analysis were vision in the better seeing eye (p<0.01) and VF-14 scores (p<0.01). Significant predictors of standard gamble utilities were also vision in the better seeing eye (p<0.01) and VF-14 scores (p<0.05).


CONCLUSIONS
Both the standard gamble and TTO methods demonstrate strong validity when evaluated against visual acuity in the better seeing eye and the VF-14 score.
Sharma
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Cost-Effective Ocular Health Policy Unit, Department of Ophthalmology, Queen's University, Hotel Dieu Hospital, Kingston, ON, Canada. sanjay-sharma60@hotmail.com
Brown
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Hollands
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Robins
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Shah
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D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D020000:Decision Support Systems, Clinical; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011788:Quality of Life; D012044:Regression Analysis; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards; D014786:Vision Disorders / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*