Going beyond health-related quality of life for outcome measurement in economic evaluation

Background: The quality-adjusted life year (QALY) framework has been challenged for use in economic evaluation because of its narrow focus on health-related aspects of quality of life, thus ignoring potential ‘non-health’ benefits associated with treatments and interventions. With the development of new preference-based measures, such as the ICEpop CAPability (ICECAP) instruments that adopt a broader evaluative space, the aim of this thesis was to examine methodological considerations and applied implications for outcome measurement in health economics when applying measures that extend beyond health. Methods: A narrative review provides an overview of challenges involved for broadening the evaluative space of the QALY and the progress that has been made in this area. A critical interpretive synthesis (CIS) is then presented that conceptualized benefits beyond the health-related QALY, followed by three empirical analyses, each using a different dataset: (i) regression analyses testing the complementarity of a preference-based health-related quality of life (HRQoL) measure, the EQ-5D-5L, and a measure of capability wellbeing for older adults, the ICECAP-O, within the context of public health; (ii) exploratory factor analyses investigating the overlap between the ICECAP-A and five preference-based HRQoL measures; and (iii) path analyses to further explore the relationship between two HRQoL measures (EQ-5D-5L and AQoL-8D) and two wellbeing measures (ICECAP-A and subjective wellbeing). Results: The CIS conceptualized non-health benefits into four themes: (i) benefits affecting a person’s wellbeing (psychological wellbeing, subjective wellbeing, empowerment, and capability wellbeing); (ii) benefits derived from the process of health care delivery; (iii) benefits beyond the affected individual; and (iv) benefits beyond the health care sector. Three key findings were made from the empirical analyses that further explored wellbeing measures. Firstly, the ICECAP-O is more sensitive to environmental features (i.e., social cohesion and street connectivity) when compared with the EQ-5D-5L; secondly, the ICECAP-A contains domains in its descriptive system that are not measured by most HRQoL measures, except for the AQoL-8D; and thirdly, HRQoL and wellbeing measures are affected in a different way by different secondary health conditions but a similar relationship was found between the ICECAP-A and AQoL-8D. Conclusion: The thesis concludes that the application of wellbeing measures in economic evaluations requires careful consideration due to the risk of double counting. The capability approach has the potential to extend the QALY but the operationalization of this approach – and other non-health benefits within or outside the QALY framework – requires further research.