A population-based follow-up study of maximal muscle strength and mobility in patients with myasthenia gravis.

It is uncertain whether residual muscle weakness in myasthenia gravis (MG) can improve, and whether it reflects deficits and disability. In a population-based follow-up study of 107 patients with MG and 50 healthy controls, maximal shoulder, knee and ankle strength was measured using isometric dynamometry and related to the quantitative MG (QMG), the MG Composite (MGC), the MG-activities of daily living (MG-ADL), the MG quality of life 15-items (QOL15) and a 400 m walk test (400MWT). During a mean follow-up of 4.6 (±0.04) years, patients improved 10.8% (P < 0.001) in isometric shoulder strength, whereas their isometric knee strength did not improve (3.2%, P = 0.151). Higher age, longer disease duration and greater baseline impairment had no negative impact. Change in isometric shoulder and knee strength did not correlate with changes in the QMG, the MG-ADL or the QOL15. Change in isometric knee strength correlated with change in the 400MWT (r = -0.357), and the 400MWT correlated with changes in the QMG (r = 0.439), the MG-ADL legs subitem (r = 0.419) and the QOL15 (r = 0.310). Overall, muscle strength improved over time, and the MG clinical scales were related to impaired mobility and muscle strength. Change in residual muscle weakness was unrelated to disability (MG-ADL) and quality of life (QOL15).

Outcome Measures in Clinical Trials of Patients With Myasthenia Gravis.

Myasthenia gravis (MG) is a heterogeneous disorder whose clinical presentation ranges from mild ocular deficits to severe widespread weakness. This variance poses a challenge when quantifying clinical deficits. Deficits and symptoms are quantified using standardized clinical scales and questionnaires which are often used as outcome measures. The past decades have seen the development of several validated outcome measures in MG, which are used in clinical trials to obtain regulatory approval. In recent years, emphasis has moved from objective assessments to patient-reported outcomes. Despite a growing body of literature on the validity of the MG-specific outcome measures, several unresolved factors remain. As several novel therapeutics are currently in clinical development, knowledge about capabilities and limitations of outcome measures is needed. In the present paper, we describe the most widely used clinical classifications and scales in MG. We highlight the choice of outcome measures in published and ongoing trials, and we denote whether trial efficacy was reached on these outcomes. We discuss advantages and limitations of the individual scales, and discuss some of the unresolved factors relating to outcome assessments in MG.