Mapping the Nottingham Health Profile onto the preference-based EuroQol-5D instrument for patients with diabetes

Abstract Objective The aim of this study was to derive a function that can map the Nottingham Health Profile (NHP) questionnaire onto a utility measure, the EuroQol five-dimensional (EQ-5D) questionnaire index, for diabetic patients. Methods A cross-sectional study was performed on diabetic patients in Hungary with different complications in which quality of life was measured by using both the NHP questionnaire and the EQ-5D questionnaire. Ordinary stepwise-backward least-squares regression was used to develop a mapping function. Adjusted R 2 , Akaike's information criterion, and root mean square error were used to assess the performance of the model. The robustness of the models was tested using 10-fold cross-validation and bootstrapping. Results The best-fitting models were those that contained all the NHP statements as predictors and a stepwise reduced version that contained only 19 statements. The latter model, however, showed considerable variability in the selection of predictors. The adjusted R 2 of the former model was 0.68, the root mean square error was 174, and the Akaike's information criterion was −559.9. Conclusions The expected value of the EQ-5D questionnaire can be reasonably predicted on the basis of results of the NHP in patients with diabetes mellitus. The mapping function of the NHP onto the EQ-5D questionnaire is capable of estimating the expected EQ-5D questionnaire utility values in a group of patients with diabetes. The function's applicability for individual-level predictions, however, is limited. Further research is needed to find out whether mapping functions developed in Central-Eastern European countries are transferable to Western European countries.