Turbulence in the system: Higher rates of left-without-being-seen emergency department visits and associations with increased risks of adverse patient outcomes since 2020.

Objective: To examine risks of severe adverse patient outcomes shortly after a left-without-being-seen emergency department (LWBS ED) visit since 2020.

Methods: In this retrospective study using linked administrative data, we examined temporal trends in monthly rates of ED and LWBS visits for adults in Ontario, Canada, 2014‒2023. In patient-level analyses restricted to the first eligible LWBS ED visit, we used modified Poisson regression to compare the composite outcome of 7-day all-cause mortality or hospitalization following a LWBS ED visit for April 1, 2022‒March 31, 2023 (recent period) to April 1, 2014‒March 31, 2020 (baseline period), adjusted for age, sex, and Charlson comorbidity index.

Results: Despite fewer monthly ED visits since 2020, temporal trends revealed sustained increases in monthly LWBS rates. LWBS ED visits after April 1, 2020 exceeded the baseline period's single-month LWBS maximum of 4.0% in 15 out of 36 months. The composite outcome of 7-day all-cause mortality or hospitalization was 3.4% in the recent period versus 2.9% in the baseline period (adjusted risk ratio [aRR] 1.14, 95% confidence interval [CI] 1.11‒1.18) and remained elevated at 30 days (6.2% vs. 5.8%, respectively; aRR 1.05, 95% CI 1.03‒1.07), despite similar rates of post-ED outpatient visits (7-day recent and baseline: 38.9% and 39.7%, respectively,  = 0.38; 30-day: 59.4% and 59.7%, respectively,  = 0.05).

Conclusions: The rate of short-term mortality or hospitalization after a LWBS ED visit has recently increased, despite fewer ED visits/month and similar proportion of post-ED outpatient encounters. This concerning signal should prompt interventions to address system- and population-level causes.