Vocal Tract Discomfort Scale-Brazil (VTDS-BR): Validation Based on Internal Consistency, Reliability, and Accuracy

Objective To validate the Vocal Tract Discomfort Scale for the Brazilian Portuguese (VTDS-BR), based on internal consistency, reliability, and accuracy. Methods The participants were 431 adults of both sexes, divided in two groups: dysphonia (DG) and vocally healthy (VHG). We built a digital database with personal, professional information and the item-by-item VTDS-BR responses of the participants. We applied Cronbach's alpha, exploratory factor analysis; confirmatory factor analysis; Item Response Theory (IRT) using the Samejima model; and ROC (Receiver Operating Characteristic) curve analysis to obtain the VTDS-BR cut-off point. Results The VTDS-BR has an eight-item structure and two factors: vocal hyperfunction without phonotraumatic injury and with phonotraumatic injury. Each item is evaluated based on two facets related to frequency and intensity, with a Likert scale response key. There are four possible answers: never, sometimes, often, and always for frequency and none, mild, moderate, and intense for intensity. We applied an IRT model, which allowed the identification of which items are more related to dysphonia, based on higher values in the parameters discrimination (a) and difficulty (b), which contributed to the calculation of each participant's aptitude for the development of voice problems, by means of a score. The cut-off value was determined using the ROC curve, in which values greater than − 1.432 indicate a higher probability of voice alterations. Conclusion VTDS-BR went through the stages of validation of internal consistency, reliability, and accuracy. It presents an 8-item, two-factor, and two-facet structure to assess frequency and intensity of vocal tract discomfort symptoms. VTDS-BR is suitable for clinical use or in screening activities, as it is quick to apply and its interpretation is indicative of people with and without phonotraumatic injury.