Purpose: A comprehensive protocol to evaluate voice quality can support a full characterisation of voice disorders and be used to plan voice interventions. The purpose of this study was to develop and validate a standardised protocol for voice assessment, contributing with a comprehensive and valuable tool for clinician practice and research.
Method: The initial structure and content of the protocol was based on an extensive literature review of existing voice assessment tools. The content validity was then assessed by a panel of voice specialist, using a modified Bland and Altman graphical method and the intraclass correlation coefficient (ICC). A group of participants with vocal pathology was finally assessed by two voice specialists on the same day (inter-rater reliability), and, on a second day, by a single evaluator (intra-rater reliability). Inter and intra-reliability were evaluated through Cohen's kappa (k) for nominal variables, and Spearman's Correlation Coefficient (ρ) for quantitative and ordinal variables.
Results: The Bland and Altman analysis, revealed a reasonable agreement between the experts and the ICC values were lower than expected, but the confidence intervals were very wide. The intra-rater reliability of the protocol's nominal variables was almost perfect, with a mean k of 0.977; inter-rater reliability of nominal variables was also almost perfect, with a mean k of 0.893. The ordinal and quantitative variables revealed a very good to excellent relationship, with a mean ρ of 0.912.
Conclusions: Evidence of content validity, high intra and inter-rater reliability of a standardised protocol for voice assessment, have been shown. This protocol can be used to assess and collect data from patients, to train voice specialists and to develop reference voice databases. It has been designed to serve voice experts with diverse backgrounds and assessment needs.
Keywords: Assessment; Protocol; Voice.
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