title: Clinical and economic factors associated with ambulance use to the emergency department.
abstract: BACKGROUND
  Concern about ambulance diversion and emergency department (ED) overcrowding has increased scrutiny of ambulance use. Knowledge is limited, however, about clinical and economic factors associated with ambulance use compared to other arrival methods.
  
  
  OBJECTIVE
  To compare clinical and economic factors associated with different arrival methods at a large, urban, academic hospital ED.
  
  
  METHODS
  This was a retrospective, cross-sectional study of all patients seen during 2001 (N = 80,209) at an urban academic hospital ED. Data were obtained from hospital clinical and financial records. Outcomes included acuity and severity level, primary complaint, medical diagnosis, disposition, payment, length of stay, costs, and mode of arrival (bus, car, air-medical transport, walk-in, or ambulance). Multivariate logistic regression identified independent factors associated with ambulance use.
  
  
  RESULTS
  In multivariate analysis, factors associated with ambulance use included: triage acuity A (resuscitation) (adjusted odds ratio [OR], 51.3; 95% confidence interval [CI] = 33.1 to 79.6) or B (emergent) (OR, 9.2; 95% CI = 6.1 to 13.7), Diagnosis Related Group severity level 4 (most severe) (OR, 1.4; 95% CI = 1.2 to 1.8), died (OR, 3.8; 95% CI = 1.5 to 9.0), hospital intensive care unit/operating room admission (OR, 1.9; 95% CI = 1.6 to 2.1), motor vehicle crash (OR, 7.1; 95% CI = 6.4 to 7.9), gunshot/stab wound (OR, 2.1; 95% CI = 1.5 to 2.8), fell 0-10 ft (OR, 2.0; 95% CI = 1.8 to 2.3). Medicaid Traditional (OR, 2.0; 95% CI = 1.4 to 2.4), Medicare Traditional (OR, 1.8; 95% CI = 1.7 to 2.1), arrived weekday midnight-8 am (OR, 2.0; 95% CI = 1.8 to 2.1), and age > or =65 years (OR, 1.3; 95% CI = 1.2 to 1.5).
  
  
  CONCLUSIONS
  Ambulance use was related to severity of injury or illness, age, arrival time, and payer status. Patients arriving by ambulance were more likely to be acutely sick and severely injured and had longer ED length of stay and higher average costs, but they were less likely to have private managed care or to leave the ED against medical advice, compared to patients arriving by independent means.
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520, USA. Jennifer.ruger@yale.edu
authors.forename: Jennifer Prah
authors.initials: JP
authors.lastname: Ruger
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Richter
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Lewis
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000552:Ambulances / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000191:economics / Q000706:statistics & numerical data*; D005260:Female; D019538:Health Care Surveys; D017721:Hospital Costs / Q000706:statistics & numerical data; D006801:Humans; D007348:Insurance, Health / Q000706:statistics & numerical data; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D008923:Missouri; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D014187:Transportation of Patients / Q000706:statistics & numerical data; D014505:Urban Population / Q000706:statistics & numerical data