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Introduction: Stroke is a common medical emergency. The outcome depends upon access to stroke specialists, rapid scanning, assessment, and treatments. Identification of large vessel occlusion (LVO) is critical in the selection of patients for emergency embolectomy (clot removal) in patients with acute ischemic stroke. A pre-hospital stroke severity scale, such as the Los Angeles Motor Scale (LAMS) may have utility in selecting appropriate patients for CTA, while minimizing radiation exposure risk to the population as a whole.Methods: This was a retrospective analysis of 249 consecutive code stroke activations at a comprehensive stroke center during a 3.5 month period using a LAMS cutoff of ≥4 to trigger CTA acquisition. We determined the sensitivity, specificity, positive predictive value, and negative predictive value of using LAMS to detect large vessel occlusion (LVO). Gold standard was any vessel imaging within 24 hours. Inter-rater reliability of LAMS scoring was determined by blinded scoring of physical exam data from the chart by 3 neurovascular physicians.Results: There were 249 code stroke activations during the study period: 91 acute CTAs were recommended based on LAMS scoring. 20 large vessel occlusions were detected. 158 patients did not have a CTA acutely; none had a LVO during subsequent vessel imaging. The sensitivity is 100%, negative predictive value 100%, specificity 69%, positive predictive value 22% of the LAMS triage method. Inter-rater Reliability: Shrout-Fleiss pairwise weighted kappa coefficients between the three raters on LAMS scores were 0.67, 0.55, and 0.62. Kappa coefficients for pairs of raters when LAMS were dichotomized as <3 vs 4-5 were 0.64, 0.50, and 0.71. Clinically meaningful disagreements were evident.Conclusions: Accuracy and ease-of-use makes LAMS an ideal clinical tool to rapidly assess acute stroke patients for LVO and emergency mechanical thrombectomy. LAMS demonstrated excellent sensitivity in excluding patients who did not have a LVO. Appropriate training is required to ensure accuracy of LAMS scoring by providers.