Evidence-based decisions in differentiating normal from dysphonic adults

Voice clinicians use a variety of measures to diagnose dysphonia, including the clinical interview, a perceptual/listening assessment, analysis of the acoustic and aerodynamic properties of the voice, and laryngeal imaging. However, the clinical judgment of the presence or absence of dysphonia is made early in the diagnostic process. Subsequent testing with voice measures is done to increase the probability that dysphonia is or is not present. The clinical usefulness of the measures used to diagnose dysphonia, beyond a clinician's initial clinical impression, has not been established.; The current investigation determined the clinical usefulness–validity and accuracy–of six voice impairment measures of body function/structure and activity/participation for differentiating normal from dysphonic adults. An observational research design was used to test the performance of twenty-six adult dysphonic participants, who varied in severity of impairment, with that of twenty-six normal adults. An operational definition of dysphonia was applied as a reference standard for correct diagnosis. Pre-test and post-test diagnostic probabilities were compared using the likelihood ratio as an index of accuracy. In addition, possible threats to test accuracy by demographic variables, relationships between body function/structure and activity/participation, and the usefulness of combining measures were examined.; Results indicated that the accuracy of the clinician's initial impression of the presence of dysphonia is improved when supplemented with a measure of body function/structure and activity/participation. Five of the six voice measures were valid for differentiating normal from dysphonic adults. Demographic variables did not threaten the accuracy of individual tests for determining dysphonic performance. There was a significant relationship between some, but not all of the impairment measures in the dysphonic sample. And, combining a measure of body function/structure with activity/participation improved the accuracy of making a correct diagnosis of dysphonia.