Cross-cultural adaptation and psychometric validation of the Multiple Sclerosis Health Literacy Questionnaire (MSHLQ): a patient-reported measure for a Spanish population

Health literacy is a key determinant of person-centred care and engagement in multiple sclerosis. The Multiple Sclerosis Health Literacy Questionnaire is a condition-specific patient-reported measure, but it has not been validated beyond its original cultural context. This study aimed to adapt this instrument for use in Spain and evaluate its measurement properties. In a cross-sectional study with a test–retest component, the questionnaire was translated and culturally adapted. A total of 388 people with multiple sclerosis completed the instrument, and 102 repeated it after a median interval of 14 days. Ceiling and floor effects, structural validity using confirmatory factor analysis, hypotheses testing for construct validity, internal consistency, and test–retest reliability were assessed. Ceiling effects (≥15% at the highest response option) occurred in 18 of 22 items, ranging from 15.21% to 77.32%. The four-factor model showed excellent fit (Comparative Fit Index = 0.971; Tucker–Lewis Index = 0.967; Root Mean Square Error of Approximation = 0.040; Standardised Root Mean Square Residual = 0.070). Correlations with health status (Spearman’s ρ = 0.07) and shared decision-making (Spearman’s ρ = 0.19) were positive and directionally consistent with expectations, although smaller than hypothesised. Several a priori hypotheses regarding known-groups validity were supported. Internal consistency ranged from 0.64 to 0.78 across subscales and was 0.88 for the total score. Test–retest reliability ranged from 0.69 to 0.87. The Spanish version showed good structural validity and reliability for assessing health literacy in multiple sclerosis. Ceiling effects and convergent correlations smaller than hypothesised highlight priorities for further evaluation.