As part of the validation of the Assessment of Quality of Life (AQoL) instrument comparisons were made between five multiattribute utility (MAU) instruments, each purporting to measure health-related quality of life (HRQoL). These were the AQoL, the Canadian Health Utilities Index (HUI) 3, the Finnish 15D, the EQ-5D (formerly the EuroQoL) and the SF6D (derived from the SF-36). The paper compares absolute utility scores, instrument sensitivity, and incremental differences in measured utility between different instruments predicted by different individuals. The AQoL predicted utilities are similar to those from the HUI3 and EQ-5D. By contrast the 15D and SF6D predict systematically higher utilities, and the differences between individuals are significantly smaller. There is some evidence that the AQoL has greater sensitivity to health states than other instruments. It is concluded that at present no single MAU instrument can claim to be the 'gold standard', and that researchers should select an instrument sensitive to the health states they are investigating. Caution should be exercised in treating any of the instrument scores as representing a trade-off between length of life and HRQoL.
The paper addresses some limitations of the QALY approach and outlines a valuation procedure that may overcome these limitations. In particular, we focus on the following issues: the distinction between assessing individual utility and assessing societal value of health care; the need to incorporate concerns for severity of illness as an independent factor in a numerical model of societal valuations of health outcomes; similarly, the need to incorporate reluctance to discriminate against patients that happen to have lesser potentials for health than others; and finally, the need to combine measurements of health-related quality of life obtained from actual patients (or former patients) with measurements of distributive preferences in the general population when estimating societal value. We show how equity weights may serve to incorporate concerns for severity and potentials for health in QALY calculations. We also suggest that for chronically ill or disabled people a life year gained should count as one and no less than one as long as the year is considered preferable to being dead by the person concerned. We call our approach 'cost-value analysis'.
This paper describes constructing the Assessment of Quality of Life (AQoL) instrument; designed to measure health-related quality of life (HRQoL), and to be the descriptive system for a multi-attribute utility instrument. Unlike previous utility instruments' descriptive systems, the AQoL's has been developed using state-of-the-art psychometric procedures. The result is a descriptive system which emphasizes five different facets of HRQoL and which can claim to have construct validity. Based on the WHO's definition of health a model of HRQoL was developed. Items were written by focus groups of doctors and the researchers. These were administered to a construction sample, comprising hospital patients, and community members chosen at random. Final construction was through an iterative process of factor and reliability analyses. The AQoL measures 5 dimensions: illness, independent living, social relationships, physical senses and psychological wellbeing. Each has three items. Exploratory factor analysis showed the dimensions were orthogonal, and each was unidimensional. Internal consistency was alpha = 0.81. Structural equation modeling explored its internal structure; the comparative fit index was 0.90. These preliminary results indicate the AQoL has the prerequisite qualities for a psychometric HRQoL instrument for evaluation; replication with a larger sample is needed to verify these findings. Scaling it for economic evaluation using utilities is being undertaken. Respondents have indicated the AQoL is easy to understand and is quickly completed. Its initial properties suggest it may be widely applicable.
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