Analysis of Insurance Type and Emergency Severity Index (ESI) Level in an Emergency Department Population: A Single-Center Prospective Observational Study.

Background Health insurance disparities are frequently cited as contributors to inefficiencies and rising costs in the United States healthcare system. While uninsured patients have historically been assumed to delay care and present with higher acuity, the increasing prevalence of government-sponsored insurance raises questions about emergency department utilization patterns across insurance groups. Objective The objective of this study is to evaluate the association between insurance type (private, government-sponsored, and uninsured) and Emergency Severity Index (ESI) level among emergency department patients. Methods This single-day prospective observational study was conducted at Henry Ford Warren Emergency Department on December 1, 2025. An a priori power calculation determined that 167 patients were required for 80% power to detect a medium effect size (Cohen's w = 0.30, α = 0.05, df = 8). All patients assigned an ESI level (1-5) with documented insurance information were included. Insurance was categorized as private, government-sponsored, or uninsured. Descriptive statistics were calculated, and a Pearson chi-square test of independence was used to assess the association between insurance type and ESI level; Cramer's V was calculated as a measure of effect size. Results A total of 203 patient encounters met the inclusion criteria: 152 (74.9%) government-sponsored, 35 (17.2%) private, and 16 (7.9%) uninsured. ESI level 3 represented the most common triage category overall (107/203, 52.7%). ESI level 3 accounted for 69 of 152 government-sponsored patients (45.4%), 27 of 35 privately insured patients (77.1%), and 11 of 16 uninsured patients (68.8%). Pearson's chi-square analysis demonstrated no statistically significant association between insurance type and ESI level (χ²(8) = 14.27, p = 0.075; p < 0.05 was required to determine statistical significance). Cramer's V was 0.187, indicating a small effect size. Conclusions No statistically significant association was identified between insurance type and emergency department acuity, as measured by ESI level, in this single-center, single-day sample. These preliminary findings do not support insurance status alone as a predictor of presentation severity; larger, multicenter studies are needed to confirm this observation.