The Psychometric Properties of the Voice Handicap Index in People With Parkinson's Disease

Background. Psychosocial impact of dysphonia in people with Parkinson disease (PD) has been described with the Voice Handicap Index (VHI); however, its psychometric properties when applied in this population are not described. Objective. The objective of this study was to examine the psychometric properties of the VHI in people with PD. Methods. A cross-sectional study of 151 subjects without cognitive impairment (90 people with PD and 61 controls) was carried out. The VHI was applied along with clinician-based (Mini Mental State Examination, Hoehn and Yahr staging, and Movement Disorder Society-Unified Parkinson's Disease Rating Scale) and patient-based (selfrated voice severity) outcome measures. The psychometric properties of the VHI analyzed were the feasibility, reliability, and construct validity. Results. The average age of the PD population studied was 67 years; 51% had a primary level of education and 81% were retired. On average, they had disease onset duration of 11 years, a mild disease stage, mild to moderate global motor disability and impairment, and a normal to mild self-rated voice severity. The psychometric attributes of the VHI demonstrated that the questionnaire is feasible (missing data less than 1%), reliable (Cronbach alpha > 0.9), and valid (71.5% of the total variance is explained by five factors, correlates with voice severity, PD disability, and impairment, and differentiates subjects with PD from subjects without PD). Conclusion. The VHI is a reliable and valid tool that can be recommended for the population under study although further work is required to investigate its utility in advanced stages of disease.