Análises custo-utilidade e a comparação de métodos alternativos de obtenção de preferências sociais por estados de saúde

Abstract

A common approach to measure benefits in cost-utility analysis is the use of Quality-Adjusted Life Years - QALY , which combines information on mortality and health-related quality of life (HRQol). The dimension of quality of life associated with different health states has usually been measured by cardinal methods in obtaining preferences. This work aims to verify the feasibility of using the ordinal approach in cost-utility and analyze evidence of the data quality and convergence between the techniques in obtaining societal preferences for health states. We analyze to what extent do the Ranking, Visual Analogue Scale and Time Trade-Off methods yield equivalent results, as of the utilities associated to health conditions as the degree of consistency. Data came from a evaluation study of the parameters for the valuation of health states from the EQ - 5D, carried out in 2011. In the field-work were investigated 3362 literate individuals aged between 18 and 64 years old living in urban areas of Minas Gerais. The probabilistic sample selected on the basis of quota sampling by age and sex has a margin of error equal to 3%. From the conditional logit regression model and some mathematical algorithms perform the transformation of ordinal information to cardinal data and compute the logical inconsistencies. The comparison of methods has been verified from measures of goodness of fit and correlation coefficients. The results suggest the feasibility of using a simple evaluation exercise. The relative tendency of health states presented by the TTO method remains in the ordinal exercise. However the use of this approach in cost-utility analysis also presents significant challenges, especially as the form of values normalization. As regard the data quality, the Time Trade-Off method produced higher inconsistency rate than other tecniques and respondents with lower levels of education and socioeconomic status produced larger numbers of inconsistent responses. In this sense, the ranking may to represent an interesting alternative to the cardinal techniques for measuring preferences for health states.