Cross-Cultural Adaptation and Psychometric Validation of the Greek Version of the Swallowing Disturbance Questionnaire (g-SDQ) in Persons with Multiple Sclerosis

Background/Objectives: Dysphagia affects approximately 45% of persons with multiple sclerosis (pwMS) and is a major cause of morbidity and mortality. The present study aimed to translate, cross-culturally adapt, and psychometrically validate the Greek version of the Swallowing Disturbance Questionnaire (g-SDQ) in pwMS. Methods: Eighty-eight adults with clinically stable MS completed the g-SDQ together with the Dysphagia in Multiple Sclerosis (DYMUS) questionnaire, the Speech Pathology-Specific Questionnaire for Persons with Multiple Sclerosis (SMS), the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) battery, and Verbal Fluency (VF) tests. All participants also underwent the 3-ounce Water Swallow Test (3oz-WST). Results: The g-SDQ showed good internal consistency (α = 0.857). Principal component analysis, supported by parallel analysis, yielded a two-component solution explaining 51.1% of the variance, although the components did not reproduce the theoretical oral/pharyngeal division. Screening discrimination against the 3oz-WST was high (AUC = 0.912, 95% CI 0.791–0.990); a cut-off of ≥6.5 yielded a sensitivity of 85.7% and a specificity of 93.2%, whereas the previously proposed cut-off of ≥11 detected only 50.0% of WST-positive participants. After false discovery rate (FDR) correction, the g-SDQ correlated significantly with the DYMUS (ρ =0.722), the SMS (ρ = 0.722), the EDSS (ρ = 0.250), and phonemic VF (ρ = −0.301), whereas associations with the SDMT, the GVLT-II, and categorical VF were weak and non-significant. Conclusions: The g-SDQ is a brief, non-invasive, and promising tool for screening dysphagia in Greek-speaking pwMS, although its cut-off and dimensional structure require confirmation in larger, independent samples.