Preferences and utilities for the symptoms of moderate to severe allergic asthma

Introduction: Patients with moderate to severe allergic asthma have persistent poorly controlled asthma despite inhaled or systemic corticosteroid therapy. New therapies are becoming more widely available to treat such patients, but their value needs to be formally assessed in an economic evaluation. Within a publicly funded health care system such an analysis should reflect societal preferences when measuring treatment benefits. The aim of this study was to elicit societal preferences for the symptom burden associated with moderate to severe allergic asthma. Method: Existing daily symptom diary data from a clinical trial were used to develop health state descriptions for evaluation in a standard gamble interview. Five health states were produced that reflected five distinct levels of control ranging from 'complete control of asthma' to 'worsening of asthma', as defined by another outcome measure. The symptom diary data were also used as attributes in a discrete choice experiment (DCE) to estimate willingness to pay for improvements in symptoms. Members of the general public (n = 101) completed the interview. Results: Thirteen participants failed the consistency checks and were excluded from the analysis. Societal utility ratings for the health states ranged from 0.71 (worsening of asthma) to 0.78 (complete control of asthma). The participants were also willing to pay 160 pound a month for the avoidance of all symptoms. Conclusions: The range of utility values (0.71-0.78) demonstrates the severity of moderate to severe allergic asthma. However the spread of scores between complete control of asthma and worsening of asthma was lower than was expected. The community sample placed only a moderate value on the avoidance of all asthma symptoms in the DCE survey. The results suggest that the community sample may not have fully understood the benefits of control over asthma symptoms and the limitations such symptoms can impose on everyday life