Evaluation of outcome measures for myasthenia gravis subgroups.

Introduction: Disease evaluation and long-term follow-up of myasthenia gravis (MG) patients rely on disease-specific measures. We evaluated four widely used MG-specific assessments, and compared the response to disease change in different MG subgroups.

Methods: We used the Cronbach's α coefficient to test reliability, Pearson correlation coefficients to test construct validity, as well as one-way ANOVA and independent-sample t-tests to access discriminant validity. Analyses of similar items between QMG and MG-ADL included paired-sample t-tests and mean score comparisons. Pearson correlation coefficients were used to describe the correlation between changes of QMG, MG-ADL, MG-QOL15r and MGC. The Wilcoxon matched-pairs signed-ranks test was performed to compare the outcomes.

Results: 872 MG patients were enrolled. QMG, MG-ADL, MG-QOL15r, and MGC all exhibited high reliability. All four scales displayed good discriminant validity according to the MGFA classification and MGC score. MG-ADL showed significant differences between patients grouped by age and gender, and MG-QOL15r showed significant differences between patients grouped by age. Analyses of similar items showed that MG-ADL achieved higher scores in bulbar items, whereas QMG produced higher scores in limb items. For patients in remission or minimal manifestation status, QMG exhibited significantly greater improvement than MG-QOL15r. In patients of MGFA I, II, III, and IV, QMG showed significantly greater improvement than MG-ADL.

Conclusions: Patient-reported scale is an important supplement for a given period. MG-ADL has a better response to severe disease, and MG-QOL15r is more comprehensive for patients in remission or minimal manifestation status.