The applicability of the dysphonia severity index and the voice handicap index in evaluating effects of voice therapy and phonosurgery.

The objective was to investigate the applicability of the Dysphonia Severity Index (DSI) and the Voice Handicap Index (VHI) in evaluating effects of intervention between groups of patients and for intrasubject differences and whether DSI and VHI are complementing measurements. Analyses of measurement data before and after intervention of 171 patients with voice disorders. The voice quality was measured objectively with the DSI. The perceived voice handicap was measured with the VHI. Three groups of patients were used: patients who had voice therapy, phonosurgery, or no intervention. DSI and VHI improved significantly after intervention in the voice therapy and the surgery group (median difference DSI 1.19 and 3.03, VHI -8 and -26, respectively). The intrasubject results were analyzed based on the test-retest variability of DSI and VHI. Significant better DSI and VHI scores after intervention were found in, respectively, 22% and 38% of the patients with voice therapy, and 56% and 78% of the patients with surgery. In the no intervention group, this was 11% and 12%. In 37% of the patients, the differences before and after intervention in DSI and VHI were in discordance. The DSI and VHI are able to show significant differences after intervention for voice disorders between groups of patients. The DSI and VHI can be used to determine a significant intrasubject result of intervention. The DSI and VHI measure each different aspects of the voice and are complementing measurements. The DSI is therefore applicable in clinical practice for objective evaluation of voice quality and the VHI for subjective evaluation of the perceived handicap by the patient self.