A new and easily used modified myasthenia gravis score.

We developed a new modified quantitative myasthenia gravis (mQMG) score which can be easily used in the condition of limited access to specific equipment.  Substitution peak expiratory flow rate for forced vital capacity, and removal of handgrip strength and speech test items were the major modifications. The new mQMG score was tested for content validity and test-retest reliability. Then 45 Myasthenia Gravis Foundation of America (MGFA) grade II-III outpatients who had been clinically stable ≥ 3 months were enrolled to analyze correlations between the mQMG score and the original quantitative myasthenia gravis (QMG) score, the mQMG score and the previously validated Thai-version myasthenia gravis quality of life score (MGQOL 15-Thai version), and the QMG score and MGQOL15-Thai version score by Spearman correlation (p < 0.05). The positive correlation coefficient between the mQMG and QMG score was very strong (r = 0.96, 95% CI, 0.93-0.98, p < 0.001), between the mQMG and MGQOL15-Thai version score was moderate (r = 0.44, 95% CI, 0.17-0.65, p = 0.003), and between the QMG and MGQOL15-Thai version score was moderate (r = 0.41, 95% CI, 0.14-0.63, p = 0.005). We thus conclude that the new mQMG score is practical for use in research and clinical care.