Validation of Stroke Network of Wisconsin Scale at Aurora Health Care System

Background—The Stroke Network of Wisconsin (SNOW) scale, previously called the Pomona scale,
was developed to predict large-vessel occlusions (LVOs) in patients with acute ischemic stroke (AIS). The
original study showed a high accuracy of this scale. We sought to externally validate the SNOW scale in an
independent cohort.
Methods—We retrospectively reviewed and calculated the SNOW scale, the Vision Aphasia and Neglect
Scale (VAN), the Cincinnati Prehospital Stroke Severity (CPSS), the Los Angeles Motor Scale (LAMS),
and the Prehospital Acute Stroke Severity Scale (PASS) for all patients who were presented within 24 hours
after onset at AHCS (14 hospitals) between January 2015 and December 2016. The predictive performance
of all scales and several National Institute of Health Stroke Scale cutoffs (≥6) were determined and compared. LVO was defined by total occlusions involving the intracranial internal carotid artery, middle cerebral artery (MCA; M1), or basilar arteries.
Results—Among 2183 AIS patients, 1381 had vascular imaging and were included in the analysis. LVO
was detected in 169 (12%). A positive SNOW scale had comparable accuracy to predict LVO and showed a
sensitivity of 0.80, specificity of 0.76, the positive predictive value (PPV) of 0.31, and negative predictive
value of 0.96 for the detection of LVO versus CPSS ≥ 2 of 0.64, 0.87, 0.41, and 0.95. A positive SNOW
scale had higher accuracy than VAN, LAMS, and PASS.