Validation of Spanish version of 15-item myasthenia gravis quality-of-life questionnaire

Objectives: The aim of this study was to achieve the translation and cross-cultural adaptation of the MG-QOL15R questionnaire into Spanish and the analysis of its psychometric properties. Materials and Methods: We recruited patients with MG, ≥18 years old, whose mother tongue was Spanish. After the translation and cross-cultural adaptation of the MG-QOL15-R, the following tests were performed: internal consistency using the Cronbach-α coefficient and corrected item-total correlations; reproducibility with a test-retest analysis using intraclass correlation coefficients; and concurrent validity using Spearman's correlation coefficient of the Spanish language MG-QOL15R-S, Myasthenia Gravis Activity of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. As an approximation to construct validity, the nonparametric Mann-Whitney U test was performed between MG-QOL15R-S scores according to the Myasthenia Gravis Foundation of America classification. Results: A total of 83 MG patients were enrolled, mean age 48.19 ± 17.25 years; 58 (69.9%) were women. The mean MG-QOL15R-S score was 11.3 ± 7.1. Cronbach-α coefficient was 0.92. Item-total correlation ranged between 0.43 and 0.75. Intraclass correlation coefficient was 0.80. The Spearman correlation coefficient was 0.637 (p-value <.001) for MG-ADL and 0.487 (p-value <.001) for QMG. Mann-Whitney U tests of the mean MG-QOL15R-S scores were significantly different according to the clinical severity (p-value <.001). Conclusions: The Spanish version of the MG-QOL15R is a valid and reliable instrument and potentially useful for measuring health-related quality of life in Spanish-speaking MG patients.