Myasthenia Gravis Impairment Index Indicates Response to Prednisone, IVIg, PLEX

boy with myasthenia gravis
boy with myasthenia gravis
The Myasthenia Gravis Impairment Index was developed to incorporate patient input at different stages of disease progression.

The Myasthenia Gravis Impairment Index (MGII) is a sensitive tool for identifying treatment response and clinical meaningful change among patients with myasthenia gravis (MG) receiving prednisone, intravenous immunoglobulin (IVIg), or plasma exchange (PLEX), according to a study published in Neurology.

A total of 95 patients with MG who were prescribed prednisone, IVIg, or PLEX were included in this analysis. To compare the sensitivity of the MGII, the investigators also included 54 control patients who received no treatment. Assessments using the MGII, Quantitative Myasthenia Gravis Score, Myasthenia Gravis Composite, and Myasthenia Gravis Activities of Daily Living occurred at baseline as well as 3 to 4 weeks after treatment.

Compared with control patients, those receiving a treatment course of prednisone, IVIg, or PLEX demonstrated a significantly greater change in MGII scores (P <.001). Patients receiving prednisone showed more change in the ocular domain when compared with IVIg/PLEX (effect size, 0.67 and 0.13, respectively; analysis of covariance P =.001). In the generalized domain, IVIg/PLEX were associated with greater change in scores compared with prednisone (effect size, 0.50 and 0.22, respectively; analysis of covariance P =.07). All relative efficiency ratios were found to be >1, which favored the MGII.

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According to the investigators, the small sample size in this study prohibited the estimation of minimal important differences, according to scores at baseline. In addition, as few patients reported worsening, calculation of minimal important differences for clinical worsening was deemed impossible.

The results of this study also indicate that the MGII subscores, specifically the ocular scores, may be useful “for clinical trials in pure ocular disease.”


Barnett C, Bril V, Kapral M, Kulkarni AV, Davis AM. Myasthenia Gravis Impairment Index: Responsiveness, meaningful change, and relative efficiency [published online November 3, 2017]. Neurology. doi:10.1212/WNL.0000000000004676