A conceptual map of health-related quality of life dimensions: key lessons for a new instrument

Abstract

Purpose: Quality-adjusted life years (QALYs) represent a critical metric in economic evaluations impacting key healthcare decisions in many countries. However, there is widespread disagreement as to which is the best of the health state utility (HSU) instruments that are designed to measure the Q in the QALY. Instruments differ in their descriptive systems as well as their valuation methodologies; that is, they simply measure different things. We propose a visual framework that can be utilized to make meaningful comparisons across HSU instruments.

Methods: The framework expands on existing HRQoL models, by incorporating four distinctive continua, and by putting HRQoL within the broader notion of subjective well-being (SWB). Using this conceptual map, we locate the five most widely used HSU-instruments (EQ-5D, SF-6D, HUI, 15D, AQoL).

Results: By individually mapping dimensions onto this visual framework, we provide a clear picture of the significant conceptual and operational differences between instruments. Moreover, the conceptual map demonstrates the varying extent to which each instrument moves outside the traditional biomedical focus of physical health, to also incorporate indicators of mental health and social well-being.

Conclusion: Our visual comparison provides useful insights to assess the suitability of different instruments for particular purposes. Following on from this comparative analyses, we extract some important lessons for a new instrument that cover the domains of physical, mental and social aspects of health, i.e. it is in alignment with the seminal 1948 WHO definition of health.

Keywords: EQ-5D; Health state utility instruments; QALYs; SF-6D.

Fig. 1

A conceptual map of health and well-being: The health dimensions included in HSU instruments, and the general life domains included in the PWI, placed in a theoretical context

Fig. 2

A conceptual map of the Health Utility Index, HUI (8 items). a Other psychological: happy/unhappy (emotions), b Other physical: dexterity

Fig. 3

A conceptual map of the 15D (14 items mapped, excluding the sex item: impact of health on sexual behaviour). a Other physical: eating, breathing, elimination

Fig. 4

A conceptual map of the EQ-5D (5 items)

Fig. 5

A conceptual map of the SF-6D. *The item Physical functioning relates to Mobility and Self care; the item Role functioning relates to Self-care and Usual activities; the item Social functioning refers to limitations in social activities, which relates to Social relationships; the item Mental health refers to Depression and ‘very nervous’ which relates to Anxiety

Fig. 6

A conceptual map of AQoL-8D. ^aOther psychological: dependence, control, coping, anger, confidence, self-worth, self-harm, happy (× 2)