Estimating a preference-based single index from the overactive bladder questionnaire
Objectives: The aim of the study is to estimate a preference-based single index for calculating quality-adjusted life years for patients with overactive bladder (OAB), based on a survey of the UK general population using the 5-dimensional health classification system OAB-5D, derived from the validated Overactive Bladder Questionnaire (OAB-q). Methods: An interview valuation survey of members of public in the South Yorkshire, UK was undertaken using the time-trade-off method. Each respondent was randomly allocated to one of 14 blocks, and valued seven states each plus the "pits" state, so that a total of 99 states were valued. A number of multivariate regression models were estimated for predicting a total of 3125 health state values defined by the classification. Models were compared and selected using a set of criteria, including overall diagnosis by adjusted R-squared, the sign and significance of individual parameter estimates, the relative size of coefficients within a given dimension and predictive ability. Results: The mean model was recommended for use in economic evaluation. Conclusion: This will permit the cost-effectiveness of new interventions to be assessed in patients with OAB using existing and future OAB-q data sets. © 2008, International Society for Pharmacoeconomics and Outcomes Research (ISPOR).