title: Volume-related differences in emergency department performance.
abstract: BACKGROUND
  Emergency departments (EDs) are an important source of care for a large segment of the population of the United States. In 2009 there were more than 136 million visits to the ED each year, and more than half of hospital admissions begin in the ED. Measurement and monitoring of emergency department performance has been prompted by The Joint Commission's patient flow standards. A study was conducted to attempt to correlate ED volume and other operating characteristics with performance on metrics.
  
  
  METHODS
  A retrospective analysis of the Emergency Department Benchmarking Alliance annual ED survey data for the most recent year for which data were available (2009) was performed to explore observed patterns in ED performance relative to size and operating characteristics. The survey was based on 14.6 million ED visits in 358 hospitals across the United States, with an ED size representation (sampling) approximating that of the Emergency Medicine Network (EM Net).
  
  
  RESULTS
  Larger EDs (with higher annual volumes) had longer lengths of stay (p < .0001), higher left without being seen rates (p < .0001), and longer door-to-physician times (p < .0001), all suggesting poorer operational performance. Operating characteristics indicative of higher acuity were associated with worsened performance on metrics and lower acuity characteristics with improved performance.
  
  
  CONCLUSIONS
  ED volume, which also correlates with many operating characteristics, is the strongest predictor of operational performance on metrics and can be used to categorize EDs for comparative analysis. Operating characteristics indicative of acuity also influence performance. The findings suggest that ED performance measures should take ED volume, acuity, and other characteristics into account and that these features have important implications for ED design, operations, and policy decisions.
authors.affiliation: Institute for Health Care Delivery Research, Intermountain Healthcare, Salt Lake City, Utah, USA. sharijwelch@gmail.com
authors.forename: Shari J
authors.initials: SJ
authors.lastname: Welch
authors.forename: James J
authors.initials: JJ
authors.lastname: Augustine
authors.forename: Li
authors.initials: L
authors.lastname: Dong
authors.forename: Lucy A
authors.initials: LA
authors.lastname: Savitz
authors.forename: Gregory
authors.initials: G
authors.lastname: Snow
authors.forename: Brent C
authors.initials: BC
authors.lastname: James
mesh_terms: D000704:Analysis of Variance; D019985:Benchmarking; D017598:Efficiency, Organizational; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014481:United States; D014850:Waiting Lists; D016526:Workload / Q000706:statistics & numerical data*