Auditory-perceptual evaluation of the degree of vocal deviation: correlation between the Visual Analogue Scale and Numerical Scale

Purpose: To analyze the intra-and inter-rater agreement for visual analog scale and numerical scale in task of sustained vowel and to determine numerical cutoff points to visual analog scale corresponding to the degrees of the numeric scale. Methods: We selected 205 samples of the usual task of the sustained vowel /a/.Six voice specialists rated the overall degree of vocal deviation, first by visual analog scale and, after two days, by the numeric scale. The results obtained by both scales were compared and the intra-and inter-rater agreement, the correlation between the scales, and the estimated cutoff points using the intraclass correlation and concordance Kappa coefficients, the Spearman coefficient, and analysis of variance, and the values of sensitivity and specificity were analyzed. Results: A strong correlation was observed between the scales. The following numerical cutoff values were found for visual analog scale corresponding to the numerical scale: neutral (degree zero) -0 to 34 mm; mild (degree one) -34.1 to 51 mm; moderate (degree two) -51.1 to 63.5 mm; intense (degree three) -63.6 to 77.5 mm; and extreme (degree four) -above 77.5 mm. Conclusion: The visual analog scale and numerical scale showed a strong correlation, being observed the greater intra-and inter-rater agreement in visual analog scale. Numerical cutoff values for visual analog scale were found. This correlation enables the comparison between the results found in the evaluation of the overall degree of vocal deviation by both scales, which are widely used in research and in the clinical speech therapy routine.