| Popis: |
In health economics benefits are often measured in terms of quality adjusted life years (QALYs), an index that combines the length of life and the health related quality of life (HRQoL) of patients. HRQoL is usually estimated using generic preference based measures (GPBMs). To ensure comparable decisions it would be recommended to use only one GPBM in all assessments, but this is not always appropriate due to validity and responsiveness problems of these measures. When this happens, bolt-ons represent a potential solution. Bolt-on research is at an early stage, and the process of how to identify and select bolt-ons is still unclear. To address this gap, this thesis examines methods for identifying and selecting bolt-on dimensions, using the EQ-5D as a case study. This thesis summarizes the results of four studies. The first study examined the performance of the 5 most commonly used GPBMs across all disease areas and conditions, using an overview of systematic reviews. The second study investigated the possibility of using factor analysis techniques to identify bolt-on dimensions. The third study explored whether it is possible to select between bolt-ons using their ability to predict differences in HRQoL. The fourth study examined whether it is possible to select between bolt-ons using preferences elicited from pairwise choices over health states. A number of important findings were made. First, GPBMs appear generally valid and responsive across many disease areas, but the quality, nature and breath of evidence makes difficult to draw definitive conclusions. Second, factor analysis techniques can be used to identify bolt-on dimensions. Exploratory and confirmatory factor analysis need to be used in conjunction. Third, bolt-ons differ in their ability to predict differences in HRQoL and for this reason they might be selected based on this information. Fourth, bolt-ons differ in terms of their impact on preferences and for this reason they might be selected based on this information. Overall, a key contribution of this thesis is to systematically examine methods for identifying and selecting bolt-ons for generic preference based measures. |
