Abstract Body: Background:
Small studies have found that patients presenting with posterior circulation ischemic strokes are more likely than patients with anterior circulation strokes to suffer a missed or delayed diagnosis in the ED. We evaluated whether probable ED stroke misdiagnosis was more common among patients subsequently hospitalized with anterior versus posterior circulation acute ischemic strokes using a large, multistate cohort.

Methods:
We conducted a retrospective cohort study using administrative claims data from the Healthcare Cost and Utilization Project on all hospital admissions and ED visits across 11 states from 2016-2021. To identify patients with a probable ED misdiagnosis, we identified stroke patients with an ED visit for a neurological complaint resulting in discharge to home (treat-and-release visit) in the 7 days preceding hospitalization for ischemic stroke. We used validated International Classification of Disease, Tenth Revision, Clinical Modification codes to identify stroke patients with anterior or posterior circulation strokes. We used logistic regression to determine the odds of misdiagnosis depending on stroke location adjusting for demographics and vascular risk factors.

Results:
We identified 264,705 ischemic stroke patients with a documented territory of brain infarction; 191,689 (72%) had anterior circulation stroke, 63,697 (24%) had posterior circulation stroke, and 11,319 (4%) had stroke involving both territories. Based on preceding ED treat-and-release visits, 1,116 (0.58%) patients with anterior circulation stroke, 944 (1.48%) patients with posterior circulation stroke, and 82 (0.72%) with stroke involving both territories had a probable ED misdiagnosis. After adjusting for demographic and vascular risk factors, posterior circulation strokes had a higher odds of probable ED misdiagnosis relative to both anterior (adjusted OR, 2.44; 95% CI, 2.23-2.66) and mixed territory cases (adjusted OR, 2.03; 95% CI, 1.62-2.55).

Conclusions:
Patients with posterior circulation stroke are over two times as likely to have a probable misdiagnosis in the week preceding their hospital admission relative to patients with anterior circulation stroke. These data highlight a disease of high diagnostic uncertainty and an opportunity for stroke quality improvement.