Disparities in emergency department outcomes by race during the 2022–2023 COVID-influenza twindemic

BACKGROUND: The 2022–2023 “twindemic” of COVID-19 and influenza has worsened emergency department (ED) overcrowding, revealing racial/ethnic disparities in emergency care. This study assessed racial differences in ED operational outcomes—specifically, discharge ED length of stay (LOS), boarding time among admitted patients, and left without being seen (LWBS) rates—and characterized disparities concentrated in the upper tails of delay distributions. METHODS: This retrospective observational study included adult ED encounters with respiratory presentations and/or laboratory-confirmed COVID-19 or influenza across 10 EDs in Michigan between September 2022 and December 2023. The primary outcomes were ED LOS at discharge, boarding of admitted patients, and LWBS. Models adjusted for covariates and ED site (fixed effects) with site-clustered standard errors; for time outcomes, log-minutes (back-transformed). Tail burden was defined as exceeding the pooled 75th percentile and the upper Tukey fence. Multiple imputations (m = 20) were used to address missing data. RESULTS: Of the 6,476 encounters, the unadjusted median LOS to discharge was 193.0 min (mins) (Black), 177.0 min (White), and 172.0 min (‘Other’). Adjusted differences from White were − 1.8 min (95% CI, − 9.5 to 6.2) for Black and + 1.9 min (− 6.5 to 10.6) for ‘Other’; the boarding differences were + 33.8 min (− 16.5 to 91.8) and + 58.1 min (− 26.1 to 164.4), respectively. The LWBS rate was 5.7% (Black) vs. 2.3% (White); the adjusted odds ratio was 0.98 (0.57–1.68) and 0.79 (0.64–1.00) after imputation (AUC 0.81). CONCLUSION: Median-based metrics obscured disparities in the upper tail of the institutions’ ED delays, specifically boarding time. Tail-aware metrics could augment standard dashboards by flagging uneven exposure to prolonged delays to drive equity-minded operational improvements.