title: Quality of Life and Asthma Symptom Control: Room for Improvement in Care and Measurement.
abstract: 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.
authors.affiliation: Department of Medicine, Institute for Heart and Lung Health, University of British Columbia, Vancouver, BC, Canada; Centre for Clinical Epidemiology and Evaluation, University of British Columbia, Vancouver, BC, Canada. Electronic address: msafavi@mail.ubc.ca.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Sadatsafavi
authors.affiliation: Canadian Centre for Applied Research in Cancer Control, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: Helen
authors.initials: H
authors.lastname: McTaggart-Cowan
authors.affiliation: Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Wenjia
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Medicine, Institute for Heart and Lung Health, University of British Columbia, Vancouver, BC, Canada; Centre for Clinical Epidemiology and Evaluation, University of British Columbia, Vancouver, BC, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Mark FitzGerald
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology* / Q000523:psychology*; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires
keywords: asthma; observational studies; quality of life; regression analysis