[Pretesting of the German Vocal Fatigue Index (VFI-D)-transcultural translation and cross validation]. / Prätestung des deutschen Vocal Fatigue Index (VFI-D) ­ transkulturelle Übersetzung und Kreuzvalidierung.

ABSTRACT

BACKGROUND: In clinical routine, vocal fatigue is a common symptom in patients with dysphonia. OBJECTIVE: The aim of this study was to conduct a transcultural translation of the Vocal Fatigue Index (VFI), a standardized subjective questionnaire. Furthermore, pretesting and prevalidation were performed in 20 subjects, with comparison to the Voice Handicap Index (VHI­9i) and the Vocal Tract Discomfort Scale (VTD). MATERIALS AND METHODS: The translation, content review, and pretest of the German Vocal Fatigue Index (VFI-D) was divided into four sections 1. transcultural translation, 2. expert voting on comprehensibility, 3. test of comprehensibility through cognitive interviews in 15 participants, 4. pretest of the VFI­D with cross validation compared to VHI­9i and VTD in 20 subjects. This process corresponds to current standards for transcultural translation and adaptation of questionnaires. RESULTS: According to expert voting and cognitive testing, the VFI­D is correct and comprehensible (intercoder reliability κ = 0.66). The factor analysis revealed three distinguishable parts VFI­D part 1 correlates strongly with VHI­9i and VTD, VFI­D part 2 with VTD only (rho ≈ 0.800 each), and VFI­D part 3 correlates only weakly with VHI­9i and VTD (rho ≈ 0.585). Thus, convergence and divergence validity are proven. CONCLUSION: The first German version of the VFI­D might be a base for further research on symptoms, causes, and treatment options in vocal fatigue. Particularly patients in voice-intensive professions may benefit.