A framework for extending the health-related quality adjusted life year by combining instruments.

Current measurement systems focus mostly on health, and not on multiple constructs of quality of life outcomes (for example health and social outcomes) together. This means we don't capture all that is of value to those receiving treatments, and to society more broadly. Recent research has explored how to extend the quality adjusted life year (QALY) beyond a narrow focus on health-related quality of life (HRQoL) aiming to improve the allocation of scarce health and social care resources. Measures of different constructs, including the EuroQol-Health and Wellbeing (EQ-HWB), and different versions of the Adult Social Care Outcomes Toolkit (ASCOT) and ICEpop CAPability (ICECAP), have been developed. Another approach to extending the health focused QALY is to combine existing descriptive systems with different foci into a single instrument. This has the advantage of using available information and allowing trade-offs between the domains of the descriptive systems to be made explicit. The aim of this paper is to propose a framework to guide this approach and outline the methodological process for generating broader descriptive systems. The first section of the paper explains the framework for combining existing instruments and discusses advantages and disadvantages. Advantages include increasing measurement sensitivity to the wider combined quality of life (QoL) impacts of many interventions and using value sets encompassing preferences that are based on trade-offs across diverse constructs. This enables values informed by impacts on broader QoL with relevance across diverse populations, to be used. Disadvantages include theoretical limitations linked to the constructs of QoL included, and practical difficulties combining instruments. The second section of the paper describes the methodological process for generating combined descriptive systems. This includes how to identify which constructs of QoL could be included, and a description of the mixed methods work required to generate a descriptive system that is psychometrically valid, and appropriate for valuation. Combining constructs of QoL from existing instruments offers a promising way to extend the QALY that differs to developing instruments de novo. Future research can use the framework outlined to develop combined instruments and explore the feasibility and wider applicability of the approach, and the use of the instruments generated in resource allocation decision making.