Abstract: Objective  To evaluate the validity and reliability of myasthenia gravis muscular endurance scale(MGMES) among myasthenia gravis(MG) patients in China.
Methods  Altogether 60 patients with myasthenia gravis were selected to receive examination and evaluation by 2-3 MG specialist physicians in accordance with Quantitative Myasthenia Gravis Score(QMGS), Myasthenia Gravis Composite(MGC), Absolute and Relative Score of MG(ARS-MG) and MGMES. As for MGMES, the internal consistency was assessed by Cronbach's α coefficient, the test-retest reliability was evaluated byintraclass correlation efficient(ICC), and the structural validity the test-retest reliability was evaluated by KMO(Kaiser-Meyer-Olkin) test, Bartlett's test of sphericity, and factor analysis. The correlation between criterion-related validity and scales was evaluated using Spearman correlation coefficient.
Results  The scale had good internal consistency(Cronbach′s α =0.854) and test-retest reliability(ICC=0.987, P＜0.01). There were 4 common factors, the cumulative variance contribution rate was 69.51%, and the construct validity was good. It was highly correlated with QMGS(r=0.806, P＜0.01), moderately correlated with MGC and ARS-MG(r=0.745, r=0.675, P＜0.01).
Conclusion  The MGMES is proven to have good validity and reliability, as it can reflect the severity of MG in a relatively comprehensive and accurate way. Thus, it can be further promoted in the clinical practice.

Key words: myasthenia gravis, muscular endurance scale, eliability