Optimising outcome assessment of voice interventions, I: reliability and validity of three self-reported scales

Abstract

There is an increasing choice of voice outcome research tools, but good comparative data are lacking. To evaluate the reliability and validity of three voice-specific, self-reported scales. Longitudinal, cohort comparison study. Two UK voice clinics: the Freeman Hospital, Newcastle upon Tyne, and the Glasgow Royal Infirmary. One hundred and eighty-one patients presenting with dysphonia. All patients completed the vocal performance questionnaire, the voice handicap index and the voice symptom scale. For comparison, each patient's voice was recorded and assessed perceptually using the grade-roughness-breathiness-aesthenia-strain scale. The reliability and validity of the three self-reported vocal performance measures were assessed in all subjects, while 50 completed the questionnaires again to assess repeatability. The results of the 170 participants with completed data sets showed that all three questionnaires had high levels of internal consistency (Cronbach's alpha = 0.81-0.95) and repeatability (voice handicap index = 0.83; vocal performance questionnaire = 0.75; voice symptom scale = 0.63). Concurrent and criterion validity were also good, although, of the grade-roughness-breathiness-aesthenia-strain subscales, roughness was the least well correlated with the self-reported measures. The vocal performance questionnaire, the voice handicap index and the voice symptom scale are all reliable and valid instruments for measuring the patient-perceived impact of a voice disorder.