Translation, Cultural Adaptation, and Validation of the Vietnamese Version of the Vocal Fatigue Index.

Objectives: The Vocal Fatigue Index (VFI) is widely used to identify vocal fatigue, but no Vietnamese version exists. This study aimed to translate the VFI into Vietnamese and evaluate its reliability and validity among primary school teachers in Vietnam.

Methods: The VFI was translated using a forward-backward method. A cross-sectional study was conducted with 339 primary school teachers. Internal consistency was assessed using Cronbach's alpha, and test-retest reliability was measured with intra-class correlation coefficients (ICC). Construct validity was evaluated using confirmatory factor analysis (CFA), and criterion validity was assessed using receiver operating characteristic (ROC) analysis, with self-reported voice problems as the reference.

Results: The mean age of participants was 39.9 years [standard deviation (SD) = 10.4], and 84.7% were female. Internal consistency was high (Cronbach's alpha = 0.93). Test-retest reliability was also good (ICC = 0.77, P < 0.001). CFA indicated that the three-factor model fit well with the data (Tucker-Lewis Index (TLI) = 0.91, comparative fit index (CFI) = 0.93, root mean squared error of approximation = 0.07, standardized root mean squared residual = 0.05). ROC analysis showed good criterion validity (area under ROC curve (AUC) = 0.80), with a cut-off score of 33 (out of 76) yielding sensitivity of 77.7% and specificity of 69.1%.

Conclusions: The Vietnamese version of the VFI demonstrates strong reliability and validity, making it a valuable tool for screening and research in Vietnam. Future studies should extend its use to other populations, including professional voice users.