The LAPSS Motor Scale (LAMS): A New Measure for Characterizing Stroke Severity in the Field
BACKGROUND: The Los Angeles Prehospital Stroke Screen (LAPSS) has been shown in a prospective, in the field validation study to identify stroke patients with high sensitivity and specificity. For prehospital clinical trials, it is desirable to develop an instrument that rapidly characterizes stroke severity (clinimetric measure) in addition to stroke recognition tools (diagnostic measure). Shortened versions of the NIHSS have been proposed for this purpose. However, a motor score derived from the LAPSS 3 item motor exam may serve this purpose more efficiently. METHODS: The LAPSS Motor Scale (LAMS) was constructed by assigning point values to LAPSS items of facial weakness (0,1), arm strength (0,1,2) and grip (0,1,2) to yield a total 0–5 scale. 87 patients enrolled in UCLA Stroke Network acute stroke clinical trials were analyzed. The presenting LAMS score was derived based on the recorded presenting NIHSS and grip exam. Correlations were calculated between the LAMS and 3 month functional outcomes, including NIHSS, modified Rankin, GOS, and Barthel Index. Predictive performance of the LAMS was compared with that of the initial full NIHSS and the 5 item shortened NIHSS (sNIHSS). Results: The average LAMS score was mean 2.6, median 2. LAMS score correlations with the 3 month functional outcome measures were highly statistically significant, and comparable to that of the longer sNIHSS and full NIHSS: 3 mo GOS - LAMS 0.55, sNIHSS 0.51, NIHSS 0.64; 3 mo BI - LAMS 0.49, sNIHSS 0.47, NIHSS 0.57; 3 mo mRS - LAMS 0.45, sNIHSS 0.54, NIHSS 0.54; 3 mo NIHSS - LAMS 0.50, sNIHSS 0.51, NIHSS 0.57. Considering dichotomized 3 mo measures, LAMS scores were markedly lower in patients destined for excellent outcome: 3 mo GOS=1, 3.4 vs 1, p<.0001 ; 3 mo mRS≤1, 3.8 vs 2.6, p=.06; 3 mo BI≥95, 3.6 vs 1.9, p<.0001; 3 mo NIHSS≤1, 2.2 vs 3.7, p<.001. Conclusions: A motor score easily and quickly derived from the Los Angeles Prehospital Stroke Screen quantitatively characterizes stroke severity in the field, and predicts functional outcomes with accuracy nearly comparable to that of the full NIHSS. Field use of the LAPSS would allow rapid identification of stroke patients and usefully delineate stroke severity.