• Billingsley Kaambwa and Julie Ratcliffe.
• Health Economics Unit, School of Medicine, Flinders University, Health Sciences Building, Bedford Park Campus, Sturt Road, Bedford Park, SA, 5042, Australia. billingsley.kaambwa@flinders.edu.au.
• Patient. 2018 Feb 1; 11 (1): 39-54.

Background And ObjectiveEconomic evaluation of healthcare treatment and services targeted at older people requires measurement of utility-based quality-of-life outcomes but it is not always possible to collect such outcome data. It may, however, be possible to estimate these outcomes using non-utility measures of quality of life where the latter have been collected. The objective of this study was to develop a regression-based algorithm to map a non-utility-based outcome, the Older People's Quality of Life brief questionnaire (OPQoL-brief), onto a utility-based outcome, the EuroQoL 5 Dimensions 5 Levels (EQ-5D-5L).MethodsThe estimation sample comprised 330 community-based Australian older people (>65 years), while the validation sample consisted of 293 older people from a separate study. Six regression techniques were employed to estimate utilities from OPQoL-brief. The predictive accuracy of 54 regression models (six regression techniques × nine model specifications) was assessed using six criteria: mean absolute error (MAE), root mean squared error (RMSE), correlation, distribution of predicted utilities, distribution of residuals, and proportion of predictions with absolute errors <0.05.ResultsThe 54 regression models predicted EQ-5D-5L utilities that performed differently when assessed by the six criteria. However, best results were obtained from an ordinary least squares (OLS) model where all 13 OPQoL-brief items were included as continuous variables (OLS 4). RMSE and MAE estimates for this model (0.2201 and 0.1638, respectively) were within the range of published estimates.ConclusionsIt is possible to predict valid utilities from OPQoL-brief using regression methods. We recommend OLS model (4) for this exercise.

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