Is the Los Angeles Motor Scale better than FAST or NIHSS for diagnosing stroke?

Compared to other options, scale system measures up favorably.

Large vessel occlusion (LVO) stroke is a major cause of morbidity and mortality in emergency patients, and prompt recognition and treatment is critical for improving outcomes.  The Los Angeles Motor Scale (LAMS) is an easy-to-use scale that is widely used by prehospital (EMS providers) and triage settings for patients with stroke symptoms. Several validated prehospital stroke scales exist in clinical use. The LAMS performs as well as or better than more extensive prehospital scales and the full NIH Stroke Scale. [1]

Calculation of the LAMS.

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THE GOOD

Why Use It

• One of several validated scales to identify LVO stroke; fast and easy to perform.
• Potentially reduces preventable transport delay from non-endovascular sites: every 30-minute delay correlates with 10% decrease in good outcome (defined by a Modified Rankin Score (mRS) 0-2 at 90 days). [2]
• Only three categories (facial droop, arm drift, grip strength). LAMS score ≥4 (out of five) increases risk of a large vascular occlusion by seven-fold. [3]
• Correlates well with NIHSS (gold standard), intensity of post-arrival treatment (among patients with acute cerebral ischemia, higher LAMS score in the field were strongly associated with receiving tissue-type plasminogen activator after arrival), and three-month functional outcome following an ischemic CVA. [3-4]

THE BAD
Limitations

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• Prehospital LAMS calculations predict three-month functional outcome less well than when calculated in the early hospital arrival time period. [4]
• Not a substitute for a comprehensive neurologic exam or NIHSS assessment.
• Sensitivity for LVO detection for a LAMS score ≥4 ranges from 67-81%. [5-6], compared with other scores (RACE [Rapid Arterial oCclusion Evaluation] Scale: 85% for scores ≥5 [7], CP-SSS [Cincinnati Prehospital Stroke Severity Scale]: 70% for scores ≥2 [8]). The newer VAN Score was found to be 100% sensitive, but did not include prehospital assessment and has yet to be prospectively validated.

THE UGLY
Misapplication

• Over-investigation: Patients with preexisting neurologic deficits may have a higher LAMS score.
• Under-investigation: LAMS score should ONLY be used for field triage to guide in grading stroke severity and need for transport to a Comprehensive Stroke Center.
• May lead to resource overutilization at comprehensive stroke centers.

Derivation Study:

Llanes JN, Kidwell CS, Starkman S, Leary MC, Eckstein M, Saver JL. The Los Angeles Motor Scale (LAMS): a new measure to characterize stroke severity in the field. Prehosp Emerg Care. 2004;8(1):46-50. PMID: 14691787.

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• Score derived from Los Angeles Prehospital Stroke Screen (LAPSS) items; 90 patients enrolled in acute stroke clinical trials and compared with the NIHSS and five-item shortened NIHSS (sNIHSS) scales.
• AUROC for three-month modified Rankin score (good functional outcome): LAMS 0.75, sNIHSS 0.69, NIHSS 0.74.

Key Validation Study:

Kim JT, Chung PW, Starkman S, et al. Field Validation of the Los Angeles Motor Scale as a Tool for Paramedic Assessment of Stroke Severity. Stroke. 2017;48(2):298-306. PMID: 28087807.

• Prospective, multi-site trial of 1,632 patients with acute stroke (ischemic and hemorrhagic) with LAMS calculated by EMS.
• Predictive accuracy (adjusted C statistic) for nondisabled three-month outcome: prehospital LAMS 0.76 (95% CI 0.74-0.78); early post-arrival LAMS 0.85 (95% CI 0.83-0.87); and early post-arrival NIHSS 0.87 (95% CI 0.85-0.88).

References:

1. Noorian AR, Sanossian N, Shkirkova K, et al. Los Angeles Motor Scale to Identify Large Vessel Occlusion: Prehospital Validation and Comparison With Other Screens. Stroke. 2018;49(3):565-572. PMID: 29459391.
2. Vagal AS, Khatri P, Broderick JP, Tomsick TA, Yeatts SD, Eckman MH. Time to angiographic reperfusion in acute ischemic stroke: decision analysis. Stroke. 2014;45(12):3625-30. PMID: 25352484.
3. Purrucker JC, Härtig F, Richter H, et al. Design and validation of a clinical scale for prehospital stroke recognition, severity grading and prediction of large vessel occlusion: the shortened NIH Stroke Scale for emergency medical services. BMJ Open. 2017;7(9):e016893. PMID: 28864702.
4. Kim JT, Chung PW, Starkman S, et al. Field Validation of the Los Angeles Motor Scale as a Tool for Paramedic Assessment of Stroke Severity. Stroke. 2017;48(2):298-306. PMID: 28087807.
5. Nazliel B, Starkman S, Liebeskind DS, et al. A brief prehospital stroke severity scale identifies ischemic stroke patients harboring persisting large arterial occlusions. Stroke. 2008;39(8):2264-7. PMID: 18556587.
6. Purrucker JC, Hametner C, Engelbrecht A, Bruckner T, Popp E, Poli S. Comparison of stroke recognition and stroke severity scores for stroke detection in a single cohort. J Neurol Neurosurg Psychiatry. 2015;86(9):1021-8. PMID: 25466259.
7. Pérez de la ossa N, Carrera D, Gorchs M, et al. Design and validation of a prehospital stroke scale to predict large arterial occlusion: the rapid arterial occlusion evaluation scale. Stroke. 2014;45(1):87-91. PMID: 24281224.
8. Kummer BR, Gialdini G, Sevush JL, Kamel H, Patsalides A, Navi BB. External Validation of the Cincinnati Prehospital Stroke Severity Scale. J Stroke Cerebrovasc Dis. 2016;25(5):1270-1274. PMID: 26971037.