Self-Assessment of Vocal Fatigue in Muscle Tension Dysphonia and Vocal Nodules: A Preliminary Analysis of the Discriminatory Potential of the Croatian Adaptation of the Vocal Fatigue Index (VFI-C)

In this paper the authors hypothesize that the intensity of subjective experience of vocal fatigue (VF) potentially reflects primary (hyper) functional vocal disorders (primary muscle tension dysphonia - MTD) differently than structural vocal disorders of functional etiology (MTD type 2a). Given the reported benefit of self-evaluation in the quantification of VF, the goal of this study was to test the potential of the Croatian adaptation of the Vocal Fatigue Index questionnaire (VFI-C) in order to show different VF intensities for the two above-mentioned diagnoses of vocal disorders. In total, 69 vocal nonprofessionals of both sexes (average age 41.5 years, +/- 13.8 years), with phoniatrically determined vocal disorders of varying etiology and 50 vocal nonprofessionals of both sexes without vocal disorders (average age 44 years, +/- 14.7 years), recruited at otorhinolaryngological clinics at medical centers in Zagreb and Split, completed the VFI-C. Psychometric characteristics of the VFI-C were determined by calculating Cronbach's alpha and the intraclass correlation coefficient, and by employing factor analysis, and the nonparametrical Mann-Whitney U test. Considering the favorable psychometric data, a descriptive analysis of the VF self-evaluation results was done for groups of participants with MTD diagnoses (10 people with an average age of 33.4, +/- 5.9 years) and vocal nodules (21 people with an average age of 37.3, +/- 12.8 years). A comparison was made of the average results of the MTD and vocal nodules groups using the nonparametric Mann-Whitney U test. Given that perceived VF was found to be greater in the MTD group, it appears that the self-evaluation of VF has a discriminatory potential for different vocal difficulties, which justifies the further verification of the complementary usefulness of VF gradation in clinical descriptions of different vocal disorders.