title: Association of age and comorbidity on 2009 influenza A pandemic H1N1-related intensive care unit stay in Massachusetts.
abstract: OBJECTIVE
  We compared comorbidity measures by age group and risk factors for influenza-like illness (ILI)-related intensive care unit (ICU) stay during the 2009 seasonal influenza and influenza A (pH1N1) pandemic.
  
  
  METHODS
  We identified all patients discharged from Massachusetts hospitals with ILI-related diagnoses between October 1, 2008, and April 25, 2009, and pH1N1-related diagnoses between April 26 and September 30, 2009. We calculated the Diagnostic Cost Group (DxCG) risk score as a measure of comorbidity. We used logistic regression predictive models to compare ICU stay predictors.
  
  
  RESULTS
  Mean DxCG scores were similar for pH1N1 and seasonal influenza time periods (0.69 and 0.70). Compared with those aged 45 to 64 years, patients younger than 5, 5 to 12, and 13 to 18 years had an increased risk of pH1N1-related ICU stay. Within the pH1N1 cohort, an asthma diagnosis was highly predictive of ICU admission among those younger than 5, 5 to 12, and 13 to 18 years, and pregnancy among those aged 26 to 44 years.
  
  
  CONCLUSIONS
  High-risk groups, including children with asthma or pregnant women, would benefit from improved surveillance and resource allocation during influenza outbreaks to prevent serious ILI-related complications.
authors.affiliation: Hilary E. D. Placzek is with the Department of Clinical and Population Health Research, University of Massachusetts Medical School (UMMS), Worcester. Lawrence C. Madoff is with the Division of Infectious Diseases and Immunology, UMMS, Worcester; the Division of Epidemiology and Immunization, Massachusetts Department of Public Health (MDPH), Boston; and ProMED-mail, International Society for Infectious Diseases, Brookline, MA.
authors.forename: Hilary E D
authors.initials: HE
authors.lastname: Placzek
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Madoff
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001249:Asthma / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D016015:Logistic Models; D008404:Massachusetts / Q000453:epidemiology; D008875:Middle Aged; D058873:Pandemics / Q000706:statistics & numerical data*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology; D012307:Risk Factors; D055815:Young Adult