Vocal Fatigue Index (VFI): Development and Validation

Objective. To develop a psychometrically sound self-report questionnaire, the Vocal Fatigue Index (VFI), to help identify individuals with vocal fatigue (VF) and characterize their complaints. Study Design. Descriptive research-scale development. Methods. Four laryngologists and six speech-language pathologists specialized in voice created a beta version of the VFI (version 1), an index of 21 statements they considered to reflect VF. Two hundred patients presenting to two different clinics completed the VFI-1. Two items from VFI-1 were excluded because of poor item-to-total correlations. The final VFI of 19 items (version 2), completed by 105 patients with voice complaints and 70 vocally healthy individuals, was assessed for its psychometric properties. Results. Test-retest reliability for the final VFI was generally strong, as was sensitivity and specificity using the classification table under logistic regression for correctly distinguishing individuals with and without VF. Moreover, factor analysis indicated that VF may be characterized by three factors: (1) factor 1, related to tiredness of voice and voice avoidance, (2) factor 2, related to physical discomfort associated with voicing, and (3) factor 3, related to improvement of symptoms with rest. Conclusion. The VFI is a standardized tool that can identify individuals with probable VF with good reliability, validity, sensitivity, and specificity.