Real-World Field Performance of the Los Angeles Motor Scale as a Large Vessel Occlusion Screen: A Prospective Muticentre Study

Abstract

Background: The Los Angeles Motor Scale (LAMS) is a 3-item, 0-to-5-point motor stroke-deficit scale derived from the Los Angeles Prehospital Stroke Screen. We assessed the predictive validity (for interventions performed and discharge disposition) of the LAMS performed in the field by paramedics in a geographic region of over 5,200 km², covering both rural and urban areas. Methods: We analyzed data gathered from Phase I of the LIT-PASS study (Large Vessel Occlusion Identification Through Prehospital Administration of Stroke Scales) which included all patients with suspected acute cerebrovascular disease, as assessed by the Balance, Eyes, Face, Arm, Speech, Terrible Headache/Time to Call 911 (BE-FAST) test. Results: Among 1,906 patients with median age 72 years (interquartile range [IQR] 60–81), 53% were female with a median on-scene time of 15 min (IQR 12–19). C statistics for the interventions of mechanical thrombectomy, alteplase administration, computed tomography angiography, and perfusion imaging were 0.681, 0.643, and 0.680, respectively. The cut point for predicting these 3 interventions was confirmed to be LAMS ≥ 4. LAMS ≥ 4 had sensitivity 0.730 (0.661–0.790) and specificity 0.570 (0.539–0.601) for mechanical intervention (endovascular thrombectomy, coiling, or clipping) and relative risk of 2.98 (2.19–4.07) for in-hospital death. Conclusions: This real-world field study validates the LAMS as an effective tool for prehospital assessment of suspected strokes in determining transport decisions, with predictive validity for interventions performed.