Introduction: The aim of the present study was the cross-cultural adaptation and validation of the Vocal Fatigue Index (VFI) in Persian. Methods: The English version of the VFI was translated to Persian using the guidelines of International Quality of Life Assessment. Eighty participants with voice disorders and 50 healthy controls without any voice disorders completed the Persian version of the VFI. The 80 participants with voice disorders completed the VFI a second time a week from the initial completion to evaluate test-retest reliability. Results: The VFI measure demonstrated a strong internal consistency. Cronbach alpha coefficient was 0.95 for tiredness and avoidance of voice use, 0.86 for physical discomfort and 0.83 for improvement or lack thereof of symptoms with voice rest. VFI also showed a high test-retest reliability (r = 0.75–0.89). Conclusions: The Persian version of the VFI is considered to be a valid and reliable questionnaire for identifying individuals with probable vocal fatigue. The VFI can be utilized in clinics across Iran in the assessment and treatment of individuals with vocal fatigue.

The Voice Foundation Vocal fatigue is a frequent symptom and a debilitating condition affecting individuals with voice disorders. In spite of the various attempts to define and quantify vocal fatigue, this complex trait has not been well understood. Mokken scaling was performed on the Vocal Fatigue Index (VFI) to develop a hierarchical understanding of the latent trait of vocal fatigue. Two hundred nine patients with voice disorders completed the VFI and provided the item responses necessary to complete the Mokken scaling. Results revealed a moderately strong Mokken scale and that the VFI presents a hierarchical structure to the underlying trait of vocal fatigue. Mokken scaling contributes to the ongoing investigation to the underlying construct of vocal fatigue and may provide additional information about specific complaints within the population of those with voice disorders.

Purpose: Vocal fatigue (VF) is a primary vocal symptom experienced by professional voice users, such as teachers, whose voice is an occupational tool. The study determines the utilization of the Vocal Fatigue Index (VFI), a 19-item scale in identifying symptoms of VF and its severity in teachers. Methods: Using responses of 695 teachers who completed the VFI, Mokken scaling was conducted on the items to identify the experiences of VF and its associated hierarchical nature of VF symptoms in teachers. Mokken scaling was completed on a total of four groups: (a) Total teachers group, (b) No VF group, (c) Low VF group, and (d) High VF group. Results: Results revealed differences in item hierarchies between total teachers and across the separate groups of VF severity. Item hierarchy for teachers highlighted items from physical discomfort at the mild end of the hierarchy to items from symptom improvement with rest at the severe end of the hierarchy. Items related to avoidance presented as a separate scale for teachers presenting with high VF. Discussion: Mokken scaling in teachers provides insight into the underlying complexity of the experience of VF symptoms and reliance on differential behavioral strategies in its management, suggesting the heterogenous nature of latent trait for VF in this specific population.

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Vocal fatigue is a frequent symptom and a debilitating condition affecting individuals with voice disorders. In spite of the various attempts to define and quantify vocal fatigue, this complex trait has not been well understood. Mokken scaling was performed on the Vocal Fatigue Index (VFI) to develop a hierarchical understanding of the latent trait of vocal fatigue. Two hundred nine patients with voice disorders completed the VFI and provided the item responses necessary to complete the Mokken scaling. Results revealed a moderately strong Mokken scale and that the VFI presents a hierarchical structure to the underlying trait of vocal fatigue. Mokken scaling contributes to the ongoing investigation to the underlying construct of vocal fatigue and may provide additional information about specific complaints within the population of those with voice disorders.