The MG Composite: A valid and reliable outcome measure for myasthenia gravis.

Journal Article

OBJECTIVE: To study the concurrent and construct validity and test-retest reliability in the practice setting of an outcome measure for myasthenia gravis (MG). METHODS: Eleven centers participated in the validation study of the Myasthenia Gravis Composite (MGC) scale. Patients with MG were evaluated at 2 consecutive visits. Concurrent and construct validities of the MGC were assessed by evaluating MGC scores in the context of other MG-specific outcome measures. We used numerous potential indicators of clinical improvement to assess the sensitivity and specificity of the MGC for detecting clinical improvement. Test-retest reliability was performed on patients at the University of Virginia. RESULTS: A total of 175 patients with MG were enrolled at 11 sites from July 1, 2008, to January 31, 2009. A total of 151 patients were seen in follow-up. Total MGC scores showed excellent concurrent validity with other MG-specific scales. Analyses of sensitivities and specificities of the MGC revealed that a 3-point improvement in total MGC score was optimal for signifying clinical improvement. A 3-point improvement in the MGC also appears to represent a meaningful improvement to most patients, as indicated by improved 15-item myasthenia gravis quality of life scale (MG-QOL15) scores. The psychometric properties were no better for an individualized subscore made up of the 2 functional domains that the patient identified as most important to treat. The test-retest reliability coefficient of the MGC was 98%, with a lower 95% confidence interval of 97%, indicating excellent test-retest reliability. CONCLUSIONS: The Myasthenia Gravis Composite is a reliable and valid instrument for measuring clinical status of patients with myasthenia gravis in the practice setting and in clinical trials.

Full Text

Duke Authors

Cited Authors

  • Burns, TM; Conaway, M; Sanders, DB; MG Composite and MG-QOL15 Study Group,

Published Date

  • May 4, 2010

Published In

Volume / Issue

  • 74 / 18

Start / End Page

  • 1434 - 1440

PubMed ID

  • 20439845

Pubmed Central ID

  • 20439845

Electronic International Standard Serial Number (EISSN)

  • 1526-632X

Digital Object Identifier (DOI)

  • 10.1212/WNL.0b013e3181dc1b1e


  • eng

Conference Location

  • United States