Voice disorders represent adverse changes in the voice, perceived through hearing. Their prevalence in the general population of the USA ranges from 6 % to 9 %, with higher percentages among older individuals and those with high vocal demands. Patients with voice disorders are treated by a team of specialists, where subjective self-assessment of the voice and the impact of voice disorders on an individual's life plays an increasingly important role in diagnostics and evaluation. One of the self-assessment questionnaires for individuals with voice disorders, statistically validated for the Slovenian language, is the Voice Handicap Index (VHI). This questionnaire, consisting of thirty items, has been translated into many languages. Due to its length, experts recognized the need for shorter versions. The latest shortened version is the Voice Handicap Index–9 International (VHI-9i), which has proven to be statistically valid and reliable in German-speaking environment.
In this master's thesis, we examined the validity and reliability of the Slovenian translation of the VHI-9i, using existing Slovenian translations of VHI items to develop the Slovenian version of the VHI-9i. The study included 112 participants of both genders and various age groups. 56 individuals with voice disorders comprised the clinical group, while 56 individuals from the general population without voice problems were included in the control group. All participants completed the Slovenian translation of the VHI-9i in printed form. Using the Mann-Whitney U test, we found a statistically significant difference in results between the clinical and control groups, with the clinical group scoring significantly worse on the questionnaire. Content validity was confirmed by three experts, and construct validity was confirmed through exploratory factor analysis. The reliability of the measurement instrument was tested using the Cronbach alpha coefficient, which was 0.871 for the entire questionnaire, indicating a very good level of reliability. The reliability of the individual subscales was also very good for the functional subscale (Cronbach alpha = 0.846) and good for the physical (Cronbach alpha = 0.613) and emotional subscales (Cronbach alpha = 0.761). Correlations between the individual subscales were also examined. The correlation between the functional and physical subscales and between the physical and emotional subscales was moderate, while the correlation between the functional and emotional subscales was high. For the clinical group, we checked the floor and ceiling effects for the entire questionnaire and found them to be absent.
We concluded that the Slovenian translation of the VHI-9i successfully differentiates between the clinical group of patients with voice disorders and the control group of healthy individuals and demonstrates sufficient validity and reliability for use in the Slovenian-speaking population.
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