Quantitative myasthenia gravis score: Assessment of responsiveness and longitudinal validity

We prospectively tested the quantitative myasthenia gravis score (QMG) for responsiveness and longitudinal construct validity in 53 patients with myasthenia gravis. Index of responsiveness was high. Longitudinal construct validity was confirmed by the correlation between changes in QMG and manual muscle testing and by a difference in QMG changes across patients that were clinically unchanged, improved, or worse between two visits. Our results support QMG use for assessing clinical change in trials.