Toward a more quantitative measure to assess severity of dysphonia posttherapy: preliminary observations

The present research compares the efficacy of using the Dysphonic Severity Percentage (DSP) scale to the equal-appearing interval scale posttherapy. The initial pretherapy investigation was conducted to determine a more quantitative measure to rate the severity of dysphonia perceptually, because rating scales have shown considerable interrater variability. The posttherapy study is a follow-up to the initial research.

The initial research involved counting the nondysphonic syllables in 10 participants with moderate-to-severe dysphonia (phonotrauma) to obtain a DSP during spontaneous speech and paragraph reading. The present posttherapy research used the same participants, the same raters, and the same method of assessment during spontaneous speech. The voice samples were both recorded and transcribed for simultaneous analysis and randomly presented to five raters, four of whom were experienced with voice disorders; one rater was a trained student. In this study, the dysphonic syllables were counted to obtain a DSP.

As in the pretherapy investigation, the DSP in the posttherapy study was found to have high interrater reliability and to be a more quantitative perceptual assessment of voice than the interval scale. Additionally, the reliability of the difference scores between pre- and posttherapy results on the Cronbach's alpha was high on the DSP scale (0.901), but dropped to 0.506 on the interval scale. Moreover, the DSP rating scale yielded greater specificity in terms of vocal improvement posttherapy than the interval scale. The interval scale tended to mask the variation in vocal improvement among participants because of the limited choices presented.