Mapping EQ-5D Utility Scores from the Incontinence Quality of Life Questionnaire among Patients with Neurogenic and Idiopathic Overactive Bladder
Kay S, Tolley K, Colayco D, Khalaf K, Anderson P, Globe D. Value Health. 2013 Mar-Apr;16(2):394-402. doi: 10.1016/j.jval.2012.12.005.

Source

Adelphi Real World, Macclesfield, UK.

Abstract

OBJECTIVES:

To provide a mapping algorithm for estimating EuroQol five-dimensional (EQ-5D) questionnaire index scores from the Incontinence-specific Quality of Life questionnaire (I-QOL) based on nationally representative samples of patients with idiopathic or neurogenic overactive bladder (OAB) using EQ-5D questionnaire preference valuations based on both the UK and US general populations.

METHODS:

Analyses were conducted for 2505 patients from the Adelphi Overactive Bladder Disease Specific Programme, a cross-sectional study of patients with idiopathic or neurogenic OAB, undertaken in the United States and Europe in 2010. A range of statistical modeling techniques was used. Tenfold cross-validation techniques were used to calculate mean absolute error (MAE) and root mean squared error (RMSE) goodness-of-fit statistics. Various predictor lists, together with a method combining stepwise selection with multivariable fractional polynomial techniques to allow nonlinear relationships to feature, were pursued.

RESULTS:

Choice of predictors was consistent for both the UK and US EQ-5D questionnaire tariffs. For idiopathic, the best model included the I-QOL total score and age (both modeled nonlinearly.) For neurogenic, the best model was the I-QOL social embarrassment domain score modeled linearly only. Best-fit results were better in the idiopathic (n = 2351; MAE = 0.10; RMSE = 0.14) than in the neurogenic sample (n = 254; MAE = 0.17; RMSE = 0.22).

CONCLUSIONS:

This research provides algorithms for mapping EQ-5D questionnaire index scores from the I-QOL, allowing calculation of appropriate preference-based health-related quality-of-life scores for use in cost-effectiveness analyses when only I-QOL data are available. The strongest results were for idiopathic patients, but those for neurogenic are consistent with those of other published mapping studies.