Quality of Life and Asthma Symptom Control: Room for Improvement in Care and Measurement

Background: The recent Global Initiative for Asthma management strategy recommends achieving symptom control and minimizing the future risk of poor outcomes as priorities for asthma management. Objective: The objective was to quantify the association between symptom control and health-related quality of life in asthma. Methods: In a prospectively recruited random sample of adults with asthma, we ascertained symptom control and measured health related quality of life using a generic (EuroQol five-dimensional questionnaire [EQ-5D]) and a disease-specific (Asthma Quality of Life Questionnaire) instrument, to estimate EQ-5D and five-dimensional Asthma Quality of Life Questionnaire (AQL-5D) utilities, respectively. We measured the adjusted difference in utilities across symptom control levels and calculated the loss of predictive efficiency due to aggregating multiple symptoms into one symptom control variable. Results: The final sample included 958 observations from 494 individuals (mean age at baseline 52.2 +/- 14.5 years; 67.0% women). Asthma was symptomatically controlled, partially controlled, and uncontrolled in 269 (28.1%), 367 (38.3%), and 322 (33.6%) observations, respectively. A person with symptomatically uncontrolled asthma would gain 0.0512 (95% CI 0.0339-0.0686) in EQ-5D or 0.0802 (95% CI 0.0693-0.0910) in AQL-5D utilities by achieving symptom control. The loss of predictive efficiency was 55.4% and 27.6% for EQ-5D and AQL-5D utilities, respectively. Conclusions: Asthma symptom control status corresponds well with both generic and disease-specific quality-of-life measures. The trade-off, however, between ease of use and predictive power should be reconsidered in developing simplified measures of control. Our results have direct relevance in informing decision analytic models of asthma and deducing the effect of interventions on quality of life through their impact on asthma control.