Trends in Emergent Interfacility Ischemic Stroke Transfers, 2016–2022

BACKGROUND AND OBJECTIVES: Interfacility transfer for emergent treatment is critical to stroke systems of care. Understanding the transfer population enables transfer system optimization. METHODS: We performed a nationwide longitudinal cross-sectional study to characterize the population emergently transferred for ischemic stroke care from 2016 to 2022. Using Medicare fee-for-service (FFS) claims, we included patients 65 years or older admitted with ischemic stroke. County-level Medicare Advantage penetration rates were used to extrapolate the results to estimate nationwide emergent transfers. Multilevel logistic regression identified features distinguishing the transferred from the nontransferred population. RESULTS: From 2016 to 2022, we identified 824,551 FFS beneficiaries (57% female) admitted for ischemic stroke: 99,751 (12%) underwent emergent transfer, while 724,800 (88%) were not transferred. The transfer population was younger (mean 78.2 years vs 80.1 years) with a higher rate of thrombectomy (15.9% vs 2.8%) and thrombolysis (24.1% vs 10.0%). Their presenting facility was more likely to be rural (55.3% vs 22.6%), have <100 beds (56.6% vs 11.9%), or be a critical access hospital (24.9% vs 2.8%). Nontransferred patients more frequently presented to a teaching facility (66.2% vs 32.3%), stroke center (83.2% vs 51.9%), or vertically integrated facility (93.5% vs 76.5%). Estimated nationwide emergent transfers increased from 2016 (21,221; 12% of admissions) to 2019 (26,720; 15%) and then decreased through 2022 (21,902; 12%). Multilevel logistic modeling showed a strong association between the transfer population and presentation to a critical access hospital (OR 2.8, 95% CI 2.4-3.3), prestroke hemiplegia (OR 2.3, 95% CI 2.3-2.4), or prestroke cerebrovascular disease (OR 2.2, 95% CI 2.2-2.3). Features associated with the nontransferred population include presentation to a facility with >400 beds (OR 0.01, 95% CI 0.01-0.01, reference ≤100 beds), a stroke center (OR 0.4, 95% CI 0.4-0.5), older age (OR 0.6, 95% CI 0.6-0.6), and more affluence (4th quartile of ADI OR 0.6, 95% CI 0.5-0.7). DISCUSSION: Emergent transfers for ischemic stroke in the United States have decreased since 2019, reversing a long-standing trend of continual increase. Receipt of thrombectomy or thrombolysis, presentation to a small facility, a nonstroke center, or in a less affluent area are associated with the transfer population.