Validation of the voice handicap index using Rasch analysis

BACKGROUND: The Voice Handicap Index is a tool for measuring the psychosocial consequences of voice disorders and consists of three dimensions. Previous psychometric evaluation of the VHI focused on the classic evaluation of reliability and validity, which is sample dependent. The authors used Rasch analysis to re-examine the dimensionality of the VHI and to produce item and scale statistics that are less sample dependent. In addition, they provide estimates of VHI item and person severities that are reported on the same logit unit scale, allowing a more straightforward interpretation of a VHI test score. PATIENTS: Dysphonic patients (N = 530), who were referred for phoniatric examination, filled out the VHI. RESULTS: Rasch analysis revealed two truly uni-dimensional constructs: the 20-item psychosocial scale and the 9-item physical-functional scale. Logit item severity measures ranged from -2.1 to +2.7. Person severity scores ranged from -4.4 to + 4.4 logits. The internal consistency of the reduced scales was similar to that of the original total VHI (0.95 and 0.84). The VHI consisted of two uni-dimensional constructs. Raw test scores can be transformed into logit unit severity measures, making the VHI more suitable for evaluating the effectiveness of voice-related therapy