The Assessment of Quality of Life (AQoL) instrument: a psychometric measure of health-related quality of life

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. Unl ike previous utility instruments' descriptive systems, the AQoL's has been developed using state-of-the-art psychometric procedures. The result is a d escriptive system which emphasizes five different facets of HRQoL and which can claim to have construct validity. Based on the WHO's definition of hea lth a model of HRQoL was developed. Items were written by focus groups of d octors and the researchers. These were administered to a construction sampl e, comprising hospital patients, and community members chosen at random. Fi nal construction was through an iterative process of factor and reliability analyses. The AQoL measures 5 dimensions: illness, independent living, soc ial relationships, physical senses and psychological wellbeing. Each has th ree items. Exploratory factor analysis showed the dimensions were orthogona l, and each was unidimensional. Internal consistency was alpha = 0.81. Stru ctural equation modeling explored its internal structure; the comparative f it index was 0.90. These preliminary results indicate the AQoL has the prer equisite qualities for a psychometric HRQoL instrument for evaluation; repl ication with a larger sample is needed to verify these findings. Scaling it for economic evaluation using utilities is being undertaken. Respondents h ave indicated the AQoL is easy to understand and is quickly completed. Its initial properties suggest it may be widely applicable.