Clinical and Economic Factors Associated with Ambulance Use to the Emergency Department

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. Objectives: 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 ≥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.