Reliability and validity of the Turkish version of the Vocal Fatigue Index

Background/aim: The aim of this study is to evaluate the reliability and validity of the Turkish version of the Vocal Fatigue Index (VFI). Materials and methods: The study was conducted with 535 participants including 285 patients with voice disorders and 250 healthy controls. Internal consistency and test-retest reliability were calculated for the reliability analysis. The mean VFI factor scores of both groups were compared. The strength and direction of the relation between VFI and Voice-Related Quality of Life (V-RQOL) measure was evaluated for the validity analysis. Results: The Cronbach's alpha coefficient of VFI factor scores was found to be 0.920 for tiredness and avoidance of voice use, 0.879 for physical discomfort with voice use, and 0.882 for improvement of symptoms with voice rest. The test-retest reliability revealed 0.877 for the tiredness and avoidance of voice use, 0.913 for the physical discomfort with voice use, and 0.820 for the improvement of symptoms with voice rest. When compared with healthy individuals, VFI factor scores were statistically significant higher in patients with voice disorders. The V-RQOL scores decreased significantly as the VFI scores increased. Conclusion: The Turkish version of the VFI is a good reliable and valid instrument for evaluating vocal fatigue symptoms in the Turkish-speaking community.