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

ABSTRACT

BACKGROUND: There is an increasing choice of voice outcome research tools, but good comparative data are lacking. OBJECTIVE: To evaluate the reliability and validity of three voice-specific, self-reported scales. DESIGN: Longitudinal, cohort comparison study. SETTING: Two UK voice clinics the Freeman Hospital, Newcastle upon Tyne, and the Glasgow Royal Infirmary. PARTICIPANTS: One hundred and eighty-one patients presenting with dysphonia. MAIN OUTCOME MEASURES: 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. RESULTS: 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. CONCLUSION: 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.