Abstract
Objectives: To standardize the Vietnamese version of the MG-ADL scale and evaluate its reliability and measurement validity in patients with myasthenia gravis. Methods: A cross-sectional descriptive study with repeated assessment in 100 patients with myasthenia gravis (MGFA classes I-IV) at Bach Mai Hospital. The scale was translated and culturally adapted following Beaton’s and WHO guidelines and administered by interview. Internal consistency was assessed with Cronbach’s alpha; test-retest reliability with ICC(2,1) in 30 patients after 3 days, together with SEM and MDC95; convergent and discriminant validity with Spearman correlation and the Kruskal-Wallis test against MGFA class; factor structure by principal component analysis with Varimax rotation, cross-checked by parallel analysis; and responsiveness in 20 patients with paired admission and discharge scores. Results: Mean age was 48.0 ± 14.7 years; 70.0% were female; anti-AChR antibodies were positive in 75.0%. Mean admission MG-ADL was 6.77 ± 4.80 (2-18), with no floor effect for the total score, although 47-63% of patients scored zero on each non-ocular item. Cronbach’s alpha was 0.843 (0.920 for the six bulbar-respiratory-motor items). ICC(2,1) was 0.976 (95% CI 0.950-0.988), with SEM = 0.74 and MDC95 = 2.04 points. Correlation with MGFA class was rho = 0.951, and scores differed across three severity groups (H = 63.75; p < 0.001). KMO was 0.813; the eigenvalue criterion extracted two components (68.15% of variance) whereas parallel analysis supported only one: the six bulbar-respiratory-motor items loaded 0.801-0.892, while the two ocular items separated with low communalities and were virtually uncorrelated (r = 0.047). MG-ADL decreased from 9.20 ± 5.16 to 5.60 ± 3.05 (p < 0.001), SRM = 1.36. Conclusions: The Vietnamese MG-ADL shows good reliability and is sensitive to clinical change, with an essentially unidimensional structure centred on the six bulbar-respiratory-motor items. Its MDC95 of approximately 2 points corresponds to the accepted minimal clinically important difference. These preliminary findings support use of the scale in Vietnam and warrant multicentre confirmation.
