The quantitative myasthenia gravis score: comparison with clinical, electrophysiological, and laboratory markers.

Author(s): Barnett C, Katzberg H, Nabavi M, Bril V.

Affiliation(s): Division of Neurology, Department of Medicine, Toronto General Hospital, University Health Network, Toronto, Canada.

Publication date & source: 2012, J Clin Neuromuscul Dis. , 13(4):201-5

OBJECTIVE: To determine whether the quantitative myasthenia gravis score (QMGS) accurately represents disease severity in patients with myasthenia gravis (MG). METHODS: One hundred thirty-five patients with MG from 2 previous randomized studies were included. QMGS correlation with the Myasthenia Gravis Foundation of America (MGFA) score, quality of life scale, acetylcholine receptor antibodies (AChRAbs), and electrophysiological parameters was studied. RESULTS: The QMGS showed a good correlation with the MGFA scale (r² = 0.54, P < 0.0001), jitter (rs = 0.40, P < 0.0001), and 15-item quality of life scale (rs = 0.41, P = 0.007) and was less well correlated with the 60-item myasthenia gravis-specific quality of life survey and other electrophysiological markers. No correlation was demonstrated with AchRAb titers, but AchRAb-positive patients had higher QMGS (14.2 ± 4.5) than AchRAb-negative patients (12.0 ± 3.7, P = 0.008). CONCLUSIONS: These results demonstrate that the QMGS is a valid marker for disease severity as shown by the MGFA scale, quality of life scale, and jitter, supporting the use of the QMGS as a primary outcome measure in clinical trials of MG.