A Brief Prehospital Stroke Severity Scale Identifies Ischemic Stroke Patients Harboring Persisting Large Arterial Occlusions
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Background and Purpose— The Los Angeles Motor Scale (LAMS) is a brief 3-item stroke severity assessment measure designed for prehospital and Emergency Department use.
Methods— The LAMS and NIHSS were scored in under-12-hour acute anterior circulation ischemic stroke patients. Stroke severity ratings were correlated with cervicocerebral vascular occlusion on CTA, MRA, and catheter angiography. Receiver operating curves, c statistics, and likelihood ratios were used to evaluate the predictive value for vascular occlusion of stroke severity ratings.
Results— Among 119 patients, mean age was 67 (±18), 45% were male. Time from onset to ED arrival was mean 190 minutes (range 10 to 660). Persisting large vessel occlusions (PLVOs) were present in 62% of patients. LAMS stroke severity scores were higher in patients harboring a vascular occlusion, median 5 (IQR 4 to 5) versus 2 (IQR 1 to 3). Similarly, NIHSS stroke severity scores were higher in PLVO patients, 19 (14 to 24) versus 5 (3 to 7). ROC curves demonstrated that the LAMS was highly effective in identifying patients with PLVOs, c statistic 0.854. At the optimal threshold of 4 or higher, LAMS scores showed sensitivity 0.81, specificity 0.89, and overall accuracy 0.85. LAMS performance was comparable to NIHSS performance (c statistic 0.933). The positive likelihood ratio associated with a LAMS score ≥4 was 7.36 and the negative likelihood ratio 0.21.
Conclusions— Stroke severity assessed by the LAMS predicts presence of large artery anterior circulation occlusion with high sensitivity and specificity. The LAMS is a promising instrument for use by prehospital personnel to identify select stroke patients for direct transport to Comprehensive Stroke Centers capable of endovascular interventions.
- Received November 19, 2007.
- Accepted December 12, 2007.