title: Defining emergency department episodes by severity and intensity: A 15-year study of Medicare beneficiaries.
abstract: BACKGROUND
  Episodes of Emergency Department (ED) service use among older adults previously have not been constructed, or evaluated as multi-dimensional phenomena. In this study, we constructed episodes of ED service use among a cohort of older adults over a 15-year observation period, measured the episodes by severity and intensity, and compared these measures in predicting subsequent hospitalization.
  
  
  METHODS
  We conducted a secondary analysis of the prospective cohort study entitled the Survey on Assets and Health Dynamics among the Oldest Old (AHEAD). Baseline (1993) data on 5,511 self-respondents >or=70 years old were linked to their Medicare claims for 1991-2005. Claims then were organized into episodes of ED care according to Medicare guidelines. The severity of ED episodes was measured with a modified-NYU algorithm using ICD9-CM diagnoses, and the intensity of the episodes was measured using CPT codes. Measures were evaluated against subsequent hospitalization to estimate comparative predictive validity.
  
  
  RESULTS
  Over 15 years, three-fourths (4,171) of the 5,511 AHEAD participants had at least 1 ED episode, with a mean of 4.5 episodes. Cross-classification indicated the modified-NYU severity measure and the CPT-based intensity measure captured different aspects of ED episodes (kappa = 0.18). While both measures were significant independent predictors of hospital admission from ED episodes, the CPT measure had substantially higher predictive validity than the modified-NYU measure (AORs 5.70 vs. 3.31; p < .001).
  
  
  CONCLUSIONS
  We demonstrated an innovative approach for how claims data can be used to construct episodes of ED care among a sample of older adults. We also determined that the modified-NYU measure of severity and the CPT measure of intensity tap different aspects of ED episodes, and that both measures were predictive of subsequent hospitalization.
authors.affiliation: Department of Health Management and Policy, College of Public Health, the University of Iowa, Iowa City, Iowa, USA. brian-kaskie@uiowa.edu
authors.forename: Brian
authors.initials: B
authors.lastname: Kaskie
authors.forename: Maksym
authors.initials: M
authors.lastname: Obrizan
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Cook
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jones
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Suzanne
authors.initials: S
authors.lastname: Bentler
authors.forename: Robert B
authors.initials: RB
authors.lastname: Wallace
authors.forename: John F
authors.initials: JF
authors.lastname: Geweke
authors.forename: Kara B
authors.initials: KB
authors.lastname: Wright
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Chrischilles
authors.forename: Claire E
authors.initials: CE
authors.lastname: Pavlik
authors.forename: Robert L
authors.initials: RL
authors.lastname: Ohsfeldt
authors.forename: Gary E
authors.initials: GE
authors.lastname: Rosenthal
authors.forename: Fredric D
authors.initials: FD
authors.lastname: Wolinsky
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006801:Humans; D007345:Insurance Claim Review; D006278:Medicare / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012720:Severity of Illness Index; D014481:United States