title: Intensive care unit admission for asthma: a marker for severe disease.
abstract: BACKGROUND
  There appears to be an asthma epidemic in the United States and other developed countries, with increasing prevalence and severity of asthma. Despite these trends, the understanding of severe asthma remains limited. Research has been hampered by the lack of clear methodology for identifying a cohort of adults with severe asthma. We systematically evaluated a method for defining a cohort of adults with severe asthma based on recent intensive care unit admissions for asthma.
  
  
  METHODS
  We used survey interview and computerized utilization data from a cohort of 400 adults with severe asthma who were enrolled after hospitalization at 17 Northern California Kaiser Permanente hospitals. To assess asthma severity, we used a multifaceted approach that combined structured telephone interview data with computerized utilization data. Using a referent group of adults who were hospitalized without intensive care unit (ICU) admission (n=282), we examined whether ICU admission is a valid marker for severe disease (n=118).
  
  
  RESULTS
  Adults with asthma who had recent ICU admission had greater severity-of-asthma scores, controlling for sociodemographic factors, smoking, and atopic history (mean score increment 2.3 points; 95% CI 1.3 to 3.2). The ICU subjects also had poorer asthma-specific quality of life (mean score increment 6.6 points; 95% CI 3.5 to 9.8) and were more likely to indicate severe self-perceived asthma (49% vs. 22%, p<0.0001). Adults with recent ICU admission were more likely to have seen an asthma specialist during the past year (27% vs. 16%). They were also more likely to have had an asthma-related emergency department visit (37% vs. 26%), hospitalization (17% vs. 6%), and ICU admission during the previous year (5% vs. 0.7%) (p<0.05 in all cases). Among the 311 adults with asthma who had continuous Kaiser Permanente pharmacy benefits for the previous 12 months, a greater proportion of the ICU group received inhaled corticosteroids during the 12 months prior to hospitalization (78% vs. 65%, p=0.024).
  
  
  CONCLUSIONS
  Admission to the ICU for asthma identifies a subgroup with severe disease, providing a valid methodology for defining a cohort of adults with severe asthma.
authors.affiliation: Division of Occupational and Environmental Medicine, Department of Medicine, University of California, San Francisco, California 94117, USA. eisner@itsa.ucsf.edu
authors.forename: Mark D
authors.initials: MD
authors.lastname: Eisner
authors.forename: Maureen
authors.initials: M
authors.lastname: Boland
authors.forename: Irina
authors.initials: I
authors.lastname: Tolstykh
authors.forename: Guillermo
authors.initials: G
authors.lastname: Mendoza
authors.forename: Carlos
authors.initials: C
authors.lastname: Iribarren
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology* / Q000628:therapy*; D015331:Cohort Studies; D003422:Critical Care; D005260:Female; D006296:Health Services / Q000706:statistics & numerical data; D006304:Health Status; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011788:Quality of Life; D012720:Severity of Illness Index