title: Validation of the MG-DIS: a disability assessment for myasthenia gravis.
abstract: This paper is aimed to present the validation of the myasthenia gravis disability assessment (MG-DIS), a MG-specific patient-reported disability outcome measure. Consecutive MG patients were enrolled, followed-up for 12 months and administered the SF-36, the WHO disability assessment schedule (WHODAS 2.0) and the preliminary 31-item MG-DIS addressing impairments and activity limitations. Factor structure and metric properties were assessed. In total, 109 patients were enrolled: 76 were females, mean age 50, mean MG duration 10.4 years, 86 were AChR-positive. The MG-DIS was reduced to 20 items, explaining 70.6 % of the original questionnaire variance, four subscales (generalized impairment-related problems; bulbar function-related problems; mental health and fatigue-related problems; vision-related problems) and an overall disability index. The MG-DIS has good metric properties (Cronbach's alpha ranging between .808 and .930), is stable, showed to be more sensitive than the WHODAS 2.0 and SF-36 to detect group differences and longitudinal changes and was well correlated with the MG-composite (.642). The MG-DIS includes items representing ocular, generalized, bulbar and respiratory symptoms, and is therefore well-built around MG-specific features. MG-DIS can be used in clinical trials as well as in observational or epidemiological studies to characterize patients' disability level and address the amount of improvement in disability. Further studies are needed to explore the possibility of a shorter disability scale.
authors.affiliation: Neurology, Public Health and Disability Unit, Neurological Institute C. Besta IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy. araggi@istituto-besta.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Raggi
authors.affiliation: Neurology, Public Health and Disability Unit, Neurological Institute C. Besta IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
authors.forename: Matilde
authors.initials: M
authors.lastname: Leonardi
authors.affiliation: Neurology, Public Health and Disability Unit, Neurological Institute C. Besta IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Schiavolin
authors.affiliation: Department of Neuroimmunology and Neuromuscular Disorders, Neurological Institute C. Besta IRCCS Foundation, Milan, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Antozzi
authors.affiliation: Department of Neuroimmunology and Neuromuscular Disorders, Neurological Institute C. Besta IRCCS Foundation, Milan, Italy.
authors.forename: Greta
authors.initials: G
authors.lastname: Brenna
authors.affiliation: Department of Neuroimmunology and Neuromuscular Disorders, Neurological Institute C. Besta IRCCS Foundation, Milan, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Maggi
authors.affiliation: Department of Neuroimmunology and Neuromuscular Disorders, Neurological Institute C. Besta IRCCS Foundation, Milan, Italy.
authors.forename: Renato
authors.initials: R
authors.lastname: Mantegazza
mesh_terms: D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology / Q000628:therapy; D057566:Self Report; D012680:Sensitivity and Specificity; D012959:Socioeconomic Factors; D016896:Treatment Outcome
keywords: Disability evaluation; Factor analysis; Myasthenia gravis; Patient-reported outcome; Validation study