SCIENCE: Validation and Psychometric Properties of the German Version of the SWAL-QOL.
The SWAL-QOL questionnaire is a common tool for evaluating patients' dysphagia-specific quality of life. A validated German version is not available. This study aimed to establish a German version of the SWAL-QOL (G-SWAL-QOL) using a standardized translation procedure and to systematically evaluate its psychometric properties. The original SWAL-QOL was translated into German following international translation guidelines. A pilot study (45 subjects) confirmed comprehensibility of the G-SWAL-QOL. A consecutive series of 158 subjects (103 patients with dysphagia; 55 healthy controls) was then recruited to assess validity and reliability of the G-SWAL-QOL. Construct validity was analyzed through a correlation analysis with both (i) the Anderson Dysphagia Inventory (ADI-D) and (ii) the Short Form 36 (SF-36). Internal consistency and test-retest reliability were evaluated to determine reliability. All questions of the G-SWAL-QOL were comprehensible, except one which was subsequently revised. Construct validity of the G-SWAL-QOL was demonstrated by moderate to high correlations with the ADI-D (Spearman's rho 0.36 - 0.88). The G-SWAL-QOL was able to differentiate between patients with dysphagia and healthy controls (p < 0.001) and was sensitive to disease severity measured by different food textures. Reliability of the G-SWAL-QOL was good to excellent for both internal consistency (Cronbach's α > 0.7 for all domains, except eating desire [α = 0.69]) and test-retest reliability (Spearman's rho ≥ 0.68 for all domains; ICC > 0.8 for all domains). The G-SWAL-QOL is a valid and reliable measuring tool for dysphagia-specific quality of life in German-speaking persons.