Abstract Body: Introduction: Understanding factors that contribute to missed diagnoses of acute ischemic stroke (AIS) may improve diagnostic accuracy. Prior studies have focused on the failure of non-neurologists to recognize AIS. The aim of this study was to understand the characteristics of stroke-alerted patients whose symptoms were misattributed to a stroke mimic by the responding vascular neurology team.

Methods: A retrospective chart review was conducted on patients seen by the vascular neurology team as a stroke alert at a single Joint-Commission-certified Comprehensive Stroke Center between 1/2021-2/2022. Patients whose symptoms were erroneously attributed to a stroke mimic at the time of assessment but later confirmed by MRI as AIS (“missed stroke”) were compared to 200 consecutive cases of stroke patients who were correctly diagnosed (“accurate stroke”) and 200 who were correctly diagnosed with a stroke mimic (“accurate mimic”). Patient characteristics were compared with univariate analysis, using chi square or Kruskal-Wallis H test as appropriate.

Results: 1823 stroke alerts were reviewed to identify 40 patients with missed stroke (incidence 2.2%) of which the median age was 66 years (IQR 58-81), median NIHSS was 5 (IQR 1-18), and 40% presented within the 4.5h-treatment window for thrombolysis. Patients with missed strokes were more likely female than those with accurate strokes (57% vs 39%, p<0.01), have a history of diabetes (43% vs 26%, p=0.03), and were more likely to receive recommendation for seizure workup (25% vs 8%, p<0.01). Compared to accurate mimics, missed strokes were significantly associated with prior substance use disorder (30% vs 11%, p<0.01) and presentation outside the 4.5h window (60% vs 40%, p<0.01). While not statistically significant, missed stroke patients were numerically more likely to be younger, non-Caucasian, have history of prior seizure, present with dizziness or encephalopathy, or be intubated.

Conclusions: Although misattribution of acute stroke symptoms to non-vascular causes by the vascular neurology team was rare, several factors distinguished missed stroke patients. These data align with prior studies that women and those with non-focal symptoms are at higher risk of misdiagnosis by non-neurologists. Education about these factors to avoid framing and anchoring biases could improve the diagnostic accuracy of the responding neurology team and, potentially, patient outcomes.