Abstract WP370: Potential of Plasma GFAP to Rule Out Minor Stroke in Low-Risk Emergency Department Patients

Introduction: Accurate emergency department (ED) diagnosis of minor stroke (NIHSS <5) can be challenging, often requiring specialist consultation and/or MRI in patients presenting with subtle neurologic complaints. ED use of Glial Fibrillary Acidic Protein (GFAP), a protein released into the blood after astrocyte injury, has potential to rule out neurologic injury in ED patients presenting with neurologic complaints. Hypothesis: GFAP may distinguish patients with acute MRI-confirmed minor stroke in the low-risk ED subpopulation (age <65 and ≤ one cardiovascular risk: smoking, diabetes, hypertension, hyperlipidemia, prior stroke or heart attack). Methods: A retrospective, single-center, observational study of ED patients with focal neurologic chief complaints from Jan 2024 to Jan 2025. Inclusion criteria: ED chief complaint of focal neurologic symptom, ED MRI brain order, and ED residual blood available. Exclusion criteria: recent stroke (12 months), intracranial hemorrhage (6 months), intracranial surgery (6 months), head trauma (7 days), or any history of brain tumor. In the MRI-confirmed stroke group, only patients with stroke center registry data were included, for accuracy of LKW time within 24 hours of blood draw and NIHSS <5 (minor stroke). Biomarker testing performed using the Quanterix Neuro 4-Plex assay. Test performance characteristics evaluated by ROC analysis with descriptive statistics. Results: 377 subjects met all inclusion and no exclusion criteria on the initial screen. 149 subsequently met all criteria for the low-risk/minor stroke group: 142 (95%) had MRI-confirmed non-stroke and 7 (5%) had MRI-confirmed acute (minor) stroke. In the low-risk/minor stroke ED population, the AUC for GFAP was 0.71 (blood drawn within 24 hours of LKW). Use of a cut-point of 25 pg/mL for GFAP had a sensitivity of 100% and a NPV of 100% to identify stroke. 26% of subjects with an MRI negative for ischemia had detectable GFAP levels below this threshold value. Discussion: In this exploratory analysis, plasma GFAP levels have potential to improve ED evaluation of patients presenting with minor focal neurologic complaints and identified at low-risk for stroke. Such identification may speed evaluation of non-stroke conditions, reduce emergent stroke team activation, and/or reduce acute neuro- imaging for stroke. Further examination in a larger ED sample is warranted to identify optimal cut-points for use and identify the ideal low-risk population.