Measuring voice outcomes: State of the science review

Researchers evaluating voice disorder interventions currently have a plethora of voice outcome measurement tools from which to choose. Faced with such a wide choice, it would be beneficial to establish a clear rationale to guide selection. This article reviews the published literature on the three main areas of voice outcome assessment: (1) perceptual rating of voice quality, (2) acoustic measurement of the speech signal and (3) patient self-reporting of voice problems. We analysed the published reliability, validity, sensitivity to change and utility of the common outcome measurement tools in each area. From the data, we suggest that routine voice outcome measurement should include (1) an expert rating of voice quality (using the Grade-Roughness-Breathiness-Asthenia-Strain rating scale) and (2) a short self-reporting tool (either the Vocal Performance Questionnaire or the Vocal Handicap Index 10). These measures have high validity, the best reported reliability to date, good sensitivity to change data and excellent utility ratings. However, their application and administration require attention to detail. Acoustic measurement has arguable validity and poor reliability data at the present time. Other areas of voice outcome measurement (e.g. stroboscopy and aerodynamic phonatory measurements) require similarly detailed research and analysis.