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Vaccines for the 21st Century: A Tool for Decisionmaking
Quality-Adjustment Weights Based on the Health Utilities Index
The committee considered two basic options for determining the quality-adjustment weights used to represent the impact of morbidity associated with the conditions under study. One option was for the committee, on the basis of its judgment and that of other experts, to assign quality-adjustment weights to each health state in each morbidity scenario associated with each condition. The other option was to use an existing generic health status assessment tool to characterize each health state. The committee chose to use a standard assessment tool to promote the comparability of the assessments for each condition. This approach also allows others who use the committee’s work to use the same instrument to make their own assessments of these or other conditions.
The committee selected the Health Utilities Index (HUI) Mark II (Feeny et al., 1995: Torrance et al., 1995). The HUI Mark II characterizes morbidity by using seven health attributes (sensation, mobility, emotion, cognition, self-care, pain, and fertility), each of which is divided into three, four, or five levels. Each level has a fixed quantitative score between 0 and 1.0 representing the strength of the “preference” for that level of morbidity relative to full health (1.0) or death (0).
A health state is described by assigning to it a specific level from each attribute. The HUI quality-adjustment weight for the health state is then derived from the following formula:
U=1.06 (b1• b2• b3• b4• b5• b6• b7)−0.06, (4)
where U is the utility of the health state (i.e., the quality weight), and bx is the score for the level assigned for attribute x (Torrance et al., 1995). U corresponds to Wi in Equation 3.
Although HUI Mark II was originally developed for a study of childhood cancer survivors, it has been adapted for use with adult populations. It has also been used with the Ontario Health Survey (Berthelot et al., 1992; Roberge et al., 1995) and the Canadian National Population Health Survey (NPHS) (Catlin and Will, 1992; Wolfson, 1996) to develop provisional estimates of age-specific health status at the population level.*
Final estimates for the NPHS will be based on the scoring system under development for the HUI Mark III, a revised HUI with eight component attributes (Torrance et al., 1992; Boyle et al., 1995).