title: Defining emergency department asthma visits for public health surveillance, North Carolina, 2008-2009.
abstract: BACKGROUND
  When using emergency department (ED) data sets for public health surveillance, a standard approach is needed to define visits attributable to asthma. Asthma can be the first (primary) or a subsequent (2nd through 11th) diagnosis. Our study objective was to develop a definition of ED visits attributable to asthma for public health surveillance. We evaluated the effect of including visits with an asthma diagnosis in primary-only versus subsequent positions.
  
  
  METHODS
  The study was a cross-sectional analysis of population-level ED surveillance data. Of the 114 North Carolina EDs eligible to participate in a statewide surveillance system in 2008-2009, we used data from the 111 (97%) that participated during those years. Included were all ED visits with an ICD-9-CM diagnosis code for asthma in any diagnosis position (1 through 11). We formed 11 strata based on the diagnosis position of asthma and described common chief complaint and primary diagnosis categories for each. Prevalence ratios compared each category's proportion of visits that received either asthma- or cardiac-related procedure codes.
  
  
  RESULTS
  Respiratory diagnoses were most common in records of ED visits in which asthma was the first or second diagnosis, while primary diagnoses of injury and heart disease were more common when asthma appeared in positions 3-11. Asthma-related chief complaints and procedures were most common when asthma was the first or second diagnosis, whereas cardiac procedures were more common in records with asthma in positions 3-11.
  
  
  CONCLUSIONS
  ED visits should be defined as asthma-related when asthma is in the first or second diagnosis position.
authors.affiliation: CB 7460, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7460. E-mail: dtravers@email.unc.edu.
authors.forename: Debbie
authors.initials: D
authors.lastname: Travers
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Kristen Hassmiller
authors.initials: KH
authors.lastname: Lich
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Lippmann
authors.affiliation: University of North Carolina, Chapel Hill, Durham Veteran's Affairs Medical Center, Durham, North Carolina.
authors.forename: Morris
authors.initials: M
authors.lastname: Weinberger
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Karin B
authors.initials: KB
authors.lastname: Yeatts
authors.affiliation: North Carolina COPD Task Force, Cary, North Carolina.
authors.forename: Winston
authors.initials: W
authors.lastname: Liao
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Anna
authors.initials: A
authors.lastname: Waller
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D039702:Current Procedural Terminology; D003953:Diagnosis-Related Groups / Q000706:statistics & numerical data; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D038801:International Classification of Diseases; D009657:North Carolina / Q000453:epidemiology; D010351:Patient Discharge / Q000706:statistics & numerical data*; D011634:Public Health; D018571:Sentinel Surveillance; D012720:Severity of Illness Index