Stroke Network of Wisconsin (SNOW) Scale Predicts Large Vessel Occlusion Stroke in the Prehospital Setting

Authors

Kessarin Panichpisal, Aurora Neuroscience Innovation Institute, Advocate Aurora HealthFollow
Sarah Erpenbeck, University of Pittsburgh School of MedicineFollow
Paul Vilar, Aurora Neuroscience Innovation Institute, Advocate Aurora HealthFollow
Reji P. Babygirija, University of Wisconsin-MadisonFollow
Maharaj Singh, Advocate Aurora Research Institute, Advocate Aurora Health; Marquette UniversityFollow
M. Riccardo Colella, Milwaukee County Office of Emergency ManagementFollow
Richard A. Rovin, Aurora Neuroscience Innovation Institute, Advocate Aurora HealthFollow

Publication Date

4-18-2022

Keywords

SNOW scale, large vessel occlusion, LVO, prehospital screening, acute ischemic stroke, endovascular thrombectomy

Abstract

Purpose: In previous trials, the Stroke Network of Wisconsin (SNOW) scale accurately predicted large vessel occlusion (LVO) stroke in the hospital setting. This study evaluated SNOW scale performance in the prehospital setting and its ability to predict LVO or distal medium vessel occlusion (DMVO) in patients suspected of having acute ischemic stroke (AIS), a scenario in which transport time to an endovascular treatment-capable facility (ECSC) is critical.

Methods: All potential AIS patients with last-known-well time of ≤ 24 hours were assessed by Milwaukee County Emergency Medical Services for LVO using SNOW. Patients with a positive SNOW score were transferred to the nearest ECSC. One such facility, Aurora St. Luke’s Medical Center (ASLMC), was the source of all patient data analyzed in this study. LVO was defined as occlusion of the intracranial carotid artery, middle cerebral artery (M1) segment, or basilar artery.

Results: From March 2018 to February 2019, 345 AIS-suspected patients were transported to ASLMC; 19 patients were excluded because no vascular imaging was performed. Of 326 patients, 32 had confirmed LVO and 21 DMVO. For identifying LVO, SNOW scale sensitivity was 0.88, specificity 0.40, positive predictive value (PPV) 0.14, negative predictive value (NPV) 0.97, and area under the curve (AUC) 0.64. Ability to predict DMVO was similar. Overall, the SNOW scale showed sensitivity of 0.83, specificity of 0.39, PPV of 0.10, NPV of 0.97, and AUC of 0.60 in identifying candidates for endovascular thrombectomy.

Conclusions: In a prehospital setting, the SNOW scale has high sensitivity in identifying candidates for endovascular thrombectomy and proved highly reliable in ruling out stroke due to LVO.

Recommended Citation

Panichpisal K, Erpenbeck S, Vilar P, Babygirija RP, Singh M, Colella MR, Rovin RA. Stroke Network of Wisconsin (SNOW) scale predicts large vessel occlusion stroke in the prehospital setting. J Patient Cent Res Rev. 2022;9:108-16. doi: 10.17294/2330-0698.1892