Patients who use emergency medical services have greater severity of illness or injury compared to those who present to the emergency department via other means: A retrospective cohort study.

Objective: We aimed to evaluate the differences in characteristics and illness/injury severity among patients who present to the emergency department (ED) via emergency medical services (EMS) compared to patients who present via other means. Methods: We analyzed a nationwide sample of ED visits from the 2015-2019 National Hospital Ambulatory Medical Care Survey. We excluded patients <18 or >92 years old, who eloped or left against medical advice, or who arrived via interfacility transport. Mode of presentation was dichotomized to those presenting to the ED via EMS versus any other mode of transportation. Using the appropriate survey sampling weights, we described patient characteristics and compared measures of illness/injury severity between groups using a multivariable logistic regression model. Results: An unweighted total of 73,397 ED visits, representing a weighted estimate of 528,083,416 ED visits in the United States during 2015-2019, included 18% arriving via EMS and 82% via other means. EMS patients were older, more often male, more often had multiple chronic medical conditions, and less often had private insurance. EMS patients had higher priority triage scores, consumed more resources in the ED, and had longer lengths of stay. Arrival by EMS was associated with higher odds of hospital admission (odds ratio [OR] 2.7, 95% confidence interval [CI] 2.4-2.9) and in-hospital mortality (OR 11.1, 95% CI 7.3-17.2). Conclusions: Patients presenting via EMS had significantly different characteristics and outcomes than those presenting via other means. These important differences should be considered when comparing studies of all ED patients versus those who present via EMS.