Background:.Quality of Life Assessment of Growth Hormone Deficiency in Adults (QoL-AGHDA) was designed for use in patients with GHD, a condition characterized amongst other things, by impairment in QoL. For use in cost-utility analysis outcomes should be measured on a scale of social preferences that assigns values of 1 and 0 to full health and dead. Condition-specific instruments may generate summary index scores but typically lack the legitimacy for use as measures of QoL outcomes in economic evaluation.
Objective. To develop item weights for QoL-AGHDA based on the social preferences of the general population as measured using EQ-5Dindex
Methods: An extended questionnaire containing all 25 items of QoL-AGHDA together with EQ-5D (a generic measure of health-related quality of life) was distributed to 1,200 individuals registered with the National Population Preference Panel. QoL-AGHDA item 'yes/no' responses were coded 1/0 respectively and entered as dummy variables in a stepwise OLS regression models in which EQ-5Dindex (a utility-weighted form of EQ-5D) was the dependent variable. The resultant regression coefficients provide estimates of the (dis)utility associated with each of the selected QoL-AGHDA items.
Results: 1024 responses were analysed. Nine individual items from the full QoL-AGHDA met the selection criteria for inclusion in the OLS model. These items included 'It takes a lot of effort for me to do simple tasks' which dominated all others with a beta-coefficient (0.276) that was 3 times greater than the next highest valued item. The individual weighted index computed using these beta-coefficients correlated well with the corresponding EQ-5D score (r2=0.476) and followed the same general pattern in discriminating between levels of self-assessed health status (excellent/very good/good/fair/poor).
Conclusions: Item weights for QOL-AGHDA, derived from the social preferences of the general population can be used to generate an index form of QoL-AGHDA that has legitimacy in cost-utility analysis.
22 - 24 Mar 2004
British Endocrine Societies