Factors Associated with Low-Acuity EMS Transport to the Emergency Department: An Observational Study Guided by the Andersen Behavioral Model

OBJECTIVES: Emergency medical services (EMS) demand is increasing, with a growing proportion of low-acuity encounters. Prior studies are limited by regional sampling, inconsistent definitions, narrow observation periods, and limited theoretical grounding. The objective of this study was to identify predisposing, enabling, and need-based factors associated with EMS transport among low-acuity emergency department (ED) patients, guided by Andersen's Behavioral Model of Health Services Use. METHODS: We conducted a secondary, retrospective observational study using a 10% random sample of multicenter electronic health record data from 21 EDs in the southeastern United States. Eligible visits included: 1) patient age >17 years, 2) occurred between January 1, 2016, and April 29, 2025, 3) triaged as Emergency Severity Index 4 or 5, and 4) ended in a final visit disposition of discharge. The primary outcome was arrival at the ED by EMS. We categorized independent variables as predisposing, enabling, or need-based factors according to Andersen's model. We used multivariable logistic regression to estimate adjusted odds ratios (aORs) with 95% confidence intervals (CIs). RESULTS: Among 41,761 low-acuity ED encounters, 3,232 (7.7%) arrived by EMS. Higher odds of EMS use were observed for older age (per 10-year increase; aOR 1.33, 95% CI = 1.30-1.36), male sex (aOR 1.20, 95% CI = 1.12-1.30), being retired or disabled (aOR 3.60, 95% CI = 3.15-4.10), being unemployed (aOR 2.26, 95% CI = 2.04-2.52), having a nighttime presentation (aOR 1.63, 95% CI = 1.51-1.76), and mental health diagnosis (aOR 1.76, 95% CI = 1.62-1.90). Lower odds of EMS arrival were observed for white race (aOR 0.89, 95% CI = 0.83-0.96), established primary care (aOR 0.57, 95% CI = 0.53-0.62), weekend presentation (aOR 0.91; 95% CI = 0.84-0.99), and visits during (aOR 0.63, 95% CI = 0.55-0.71) or after (aOR 0.54, 95% CI = 0.48-0.61) the COVID-19 period. Rurality, insurance, and primary language were not associated with EMS use. CONCLUSIONS: Among low-acuity ED patients, EMS arrival was associated with older age, unemployment or disability, no established primary care clinician, and a previous mental health diagnosis. These characteristics identify a population that may be served by alternatives to ambulance transport, such as treat-in-place and alternative destination pathways, when paired with expanded access to primary care and behavioral health resources.