title: Mortality, admission rates and outpatient use among frequent users of emergency departments: a systematic review.
abstract: OBJECTIVE
  This systematic review examines whether frequent emergency department (ED) users experience higher mortality, hospital admissions and outpatient visits than non-frequent ED users.
  
  
  METHODS
  We published an a priori study protocol in PROSPERO. Our search strategy combined terms for 'frequent users' and 'emergency department'. At least two independent reviewers screened, selected, assessed quality and extracted data. Third-party adjudication resolved conflicts. Results were synthesised based on median effect sizes.
  
  
  METHODS
  We searched seven electronic databases with no limits and performed an extensive grey literature search.
  
  
  METHODS
  We included observational analytical studies that focused on adult patients, had a comparison group of non-frequent ED users and reported deaths, admissions and/or outpatient outcomes.
  
  
  RESULTS
  The search strategy identified 4004 citations; 374 were screened by full text and 31 cohort and cross-sectional studies were included. Authors used many different definitions to describe frequent users; the overall quality of the included studies was moderate. Across seven studies examining mortality, frequent users had a median 2.2-fold increased odds of mortality compared with non-frequent users. Twenty-eight studies assessing hospital admissions found a median increased odds of admissions per visit at 1.16 and of admissions per patient at 2.58. Ten studies reported outpatient visits with a median 2.65-fold increased risk of having at least one outpatient encounter post-ED visit.
  
  
  CONCLUSIONS
  Frequent ED users appear to experience higher mortality, hospital admissions and outpatient visits compared with non-frequent users, and may benefit from targeted interventions. Standardised definitions to facilitate comparable research are urgently needed.
  PROSPERO (CRD42013005855).
authors.affiliation: RCPS Emergency Medicine Residency Program, Department of Emergency Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Moe
authors.affiliation: Emergency Medicine Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Scott
authors.initials: S
authors.lastname: Kirkland
authors.affiliation: Respiratory Health Strategic Clinical Network, Alberta Health Services, Edmonton, Alberta, Canada.
authors.forename: Maria B
authors.initials: MB
authors.lastname: Ospina
authors.affiliation: J. W. Scott Health Sciences Library, 2K4.01 WC Mackenzie Health Sciences Centre, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Sandy
authors.initials: S
authors.lastname: Campbell
authors.affiliation: Emergency Medicine Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Long
authors.affiliation: Emergency Medicine Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Alan
authors.initials: A
authors.lastname: Davidson
authors.affiliation: Emergency Medicine Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Duke
authors.affiliation: Emergency Medicine Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Tomo
authors.initials: T
authors.lastname: Tamura
authors.affiliation: Department of Emergency Medicine, University of Alberta Hospital, 1G1.42 Walter C. Mackenzie Centre, Edmonton, Alberta, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Trahan
authors.affiliation: Department of Emergency Medicine, University of Alberta Hospital, 1G1.42 Walter C. Mackenzie Centre, Edmonton, Alberta, Canada.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Rowe
mesh_terms: D017677:Age Distribution; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D000069342:Medical Overuse / Q000706:statistics & numerical data*; D009026:Mortality; D010044:Outpatient Clinics, Hospital / Q000706:statistics & numerical data*
keywords: emergency care systems, efficiency; emergency care systems, emergency departments; emergency department; management, cost efficiency; management, emergency department management