The Los Angeles Motor Scale (LAMS) as a Prehospital Triage Tool for Patients with Suspected Large Cerebral Artery Occlusion

Introduction. Routing patients with large cerebral artery occlusions to specialized centers is a critical aspect of stroke care, improving clinical outcomes after thrombectomy (TE). Clinical scales, such as the Los Angeles Motor Scale (LAMS), are the most accessible prehospital screening tools for patients selection for endovascular centers, but their real-world effectiveness requires validation.

The aim of the study — to evaluate the diagnostic accuracy of the LAMS for detecting acute large cerebral vessels occlusions (LVO) within the Moscow stroke network.

Materials and methods. The study included 336 patients with suspected stroke assessed by emergency medical services (EMS) using LAMS. LVO were confirmed in-hospital via CT angiography. Sensitivity and specificity were calculated for LAMS thresholds of 4–5 points, accompanied by ROC analysis. Retrospective LAMS scoring based on initial neurological examination was also analyzed.

Results. Sensitivity and specificity of LAMS were 50.47 % and 76.86 %, respectively. Performance varied with time since symptoms onset: <2 hours — 41.51 % and 63.53 %; 2–6 hours — 57.14 % and 81.94 %; >6 hours — 61.54 % and 87.50 %. Retrospective LAMS assessment based on in-hospital neurological examination had 72.90 % sensitivity and 77.73 % specificity. ROC analysis revealed higher predictive value for retrospective scoring (AUC = 0.80; 95 % CI — 0.75–0.85) compared to prehospital assessment (AUC = 0.67; 95 % CI — 0.61–0.73).

Conclusion. LAMS can identify patients at high risk of LVO, but its accuracy is limited within the first two hours after symptoms onset. Low early sensitivity necessitates adjustments to routing algorithms. Discrepancies between prehospital and retrospective in-hospital assessments may indicate the advisability of targeted training programs for EMS physicians to optimize LAMS application.

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