Validation of the Besta Neurological Institute rating scale for myasthenia gravis.

INTRODUCTION

We validated the scale for myasthenia gravis (MG) developed at the Neurological Institute Foundation of Milan (INCB-MG scale).

METHODS

A total of 174 patients were evaluated with the INCB-MG and compared with the MG Composite (MGC) as the gold standard. Dimensionality, reliability, and validity of the INCB-MG scale were studied by principal component factor analysis, Cronbach alpha, and Pearson correlation coefficients; interobserver reliability was calculated by the weighted Cohen K coefficient.

RESULTS

Generalized and bulbar INCB-MG subscales were unidimensional with excellent consistency; the INCB-MG and MGC scales were strongly correlated. Fatigability assessment was correlated with the INCB-MG generalized, bulbar, and respiratory subscales.

CONCLUSIONS

The INCB-MG scale is a reliable tool to assess MG and is strongly correlated with the MGC. The INCB-MG scale is a valid tool for every day practice and should be further investigated for its application in clinical trials.