title: The 4-hour standard is a meaningful quality indicator: correlation of performance with emergency department crowding.
abstract: BACKGROUND
  The 4-h standard performance is a controversial quality indicator. Crowding in emergency departments (EDs) causes increased patient morbidity and mortality. The aim of this study was to investigate the relationship between 4-h standard performance and ED crowding as measured by occupancy.
  
  
  METHODS
  A retrospective observational study was carried out using the computerized Emergency Department Information System. Daily occupancy was considered in three ways: as minutes per day spent at occupancy thresholds of 70, 80, 90 and 100%; as the peak occupancy of resuscitation and majors beds at any point in the day; and as a percentage of the total potential ED bed minutes used during the day.
  
  
  RESULTS
  An inverse relationship was observed between occupancy and 4-h standard performance using each method. Performance could be sustained at 70% occupancy, but deteriorated in a linear manner at a progressively increasing rate at 80, 90 and 100% occupancy (all P<0.01). A stepwise decrease in the mean performance was observed with increasing peak occupancy (P<0.001). A similar decrease in performance was observed with increasing 24-h overall occupancy (P<0.001).
  
  
  CONCLUSIONS
  This study has identified a clear and consistent correlation between ED crowding and performance against the 4-h standard. Because crowding is associated with harm, the 4-h standard is a meaningful quality metric for UK hospitals. Systematic measurement of ED crowding using occupancy may play a role in improving the quality of care delivered within the urgent care system.
authors.affiliation: aEmergency Department bPerformance Information Team, Derriford Hospital cCentre for Clinical Trials and Population Studies, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth dAcademic Department of Military Emergency Medicine, Royal Centre for Defence Medicine (Research & Academia), Medical Directorate, Birmingham, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Higginson
authors.forename: Anthony
authors.initials: A
authors.lastname: Kehoe
authors.forename: Justin
authors.initials: J
authors.lastname: Whyatt
authors.forename: Jason E
authors.initials: JE
authors.lastname: Smith
mesh_terms: D003441:Crowding; D004636:Emergency Service, Hospital / Q000592:standards; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D019984:Quality Indicators, Health Care / Q000592:standards; D012189:Retrospective Studies; D013997:Time Factors; D014481:United States