Leida M Lamers1. 1. Institute for Medical Technology Assessment/Department of Health Policy and Management, Erasmus University Medical Center Rotterdam, The Netherlands. l.lamers@erasmusmc.nl
Abstract
BACKGROUND: Utilities for health are measured on an interval scale, where 1 refers to full health and 0 refers to death. No theoretical lower boundary on the utilities for states worse than death exists. As a consequence, negative values receive greater weight in the calculation of mean utilities. To avoid this, negative values often are bound at -1. OBJECTIVE: The objective of this study was to compare the effect of 3 methods to bound negative values at -1 on the estimation of EQ-5D value sets: truncation, monotonic, and linear transformation. METHOD: Data of the Dutch EQ-5D valuation study were used. A total of 298 respondents directly valued 17 EQ-5D health states using the time trade-off (TTO) method. Random effects regression analysis was used to interpolate TTO values for all possible EQ-5D states. In the regression analysis the dependent variable is 1 minus the TTO value and the independent variables describe the health state. Two widely used models to estimate EQ-5D value were applied after truncation of negative values and monotonic and linear transformation of negative values. Both models also were estimated on medians. RESULTS: Truncation of negative values gave the largest mean absolute error (MAE); the linear transformation resulted in the smallest MAE. When medians were used for estimation, the MAEs were comparable with the estimation on means. CONCLUSION: The choice of a method to bound negative values is arbitrary and affects the resulting value set. For the estimation of EQ-5D value sets from a societal perspective the use of medians should be considered.
BACKGROUND: Utilities for health are measured on an interval scale, where 1 refers to full health and 0 refers to death. No theoretical lower boundary on the utilities for states worse than death exists. As a consequence, negative values receive greater weight in the calculation of mean utilities. To avoid this, negative values often are bound at -1. OBJECTIVE: The objective of this study was to compare the effect of 3 methods to bound negative values at -1 on the estimation of EQ-5D value sets: truncation, monotonic, and linear transformation. METHOD: Data of the Dutch EQ-5D valuation study were used. A total of 298 respondents directly valued 17 EQ-5D health states using the time trade-off (TTO) method. Random effects regression analysis was used to interpolate TTO values for all possible EQ-5D states. In the regression analysis the dependent variable is 1 minus the TTO value and the independent variables describe the health state. Two widely used models to estimate EQ-5D value were applied after truncation of negative values and monotonic and linear transformation of negative values. Both models also were estimated on medians. RESULTS: Truncation of negative values gave the largest mean absolute error (MAE); the linear transformation resulted in the smallest MAE. When medians were used for estimation, the MAEs were comparable with the estimation on means. CONCLUSION: The choice of a method to bound negative values is arbitrary and affects the resulting value set. For the estimation of EQ-5D value sets from a societal perspective the use of medians should be considered.
Authors: Gabrielle van der Velde; Sheilah Hogg-Johnson; Ahmed M Bayoumi; Pierre Côté; Hilary Llewellyn-Thomas; Eric L Hurwitz; Murray Krahn Journal: Qual Life Res Date: 2010-03-27 Impact factor: 4.147
Authors: Federico Augustovski; Lucila Rey-Ares; Vilma Irazola; Osvaldo Ulises Garay; Oscar Gianneo; Graciela Fernández; Marcelo Morales; Luz Gibbons; Juan Manuel Ramos-Goñi Journal: Qual Life Res Date: 2015-08-05 Impact factor: 4.147