Mapping the KDQoL-36 onto the EQ-5D-5L Utility Index in Patients undergoing Haemodialysis

Objectives

Although widely used as a tool to measure quality of life, the Kidney Disease Quality-of-Life Questionnaire (KDQoL-36) does not include a measure of health utility that would enable economic analyses to be performed. This study aimed to map the KDQoL-36 onto the EQ-5D-5L utility index for patients with end-stage kidney disease undergoing hemodialysis.

Methods

For the development of the mapping function, data from a randomized controlled trial in the United Kingdom were used and consisted of 6603 observations. Two modeling techniques were applied: (1) linear regression with fixed effects and (2) adjusted limited dependent variable mixture model (ALDVMM). Several model specifications were tested, and the preferred model was chosen based on a catalog of performance indicators. The validation phase involved applying a selection of the top-performing models to an independent UK data set consisting of 117 observations.

Results

The ALDVMM model with 3 components, using 5 domains; physical component score, mental component score, burden, symptoms, and effects, as well as age and sex as explanatory variables, was the preferred model during the estimation phase. The validation phase supported this result because the 3 component ALDVMM was the highest performing model. This model dominated in all aspects of predictive performance.

Conclusions

This novel mapping function translates the KDQoL-36 to EQ-5D-5L values in patients with end-stage kidney disease undergoing hemodialysis, using data from the United Kingdom. They demonstrate satisfactory fit and precision, providing valuable tools for clinicians and researchers, particularly in situations in which generic preference-based health-related quality-of-life instruments are inaccessible for utility derivation in cost-effectiveness studies.