Effect of geographical and ethnic variation on Dysphonia Severity Index: a study of Indian population.

Dysphonia Severity Index (DSI) is a widely used multiparametric approach to objectively quantify the voice quality. Few research groups have investigated the test-retest, interobserver variability, and influence of age and gender. They have also verified the application of DSI in various voice rehabilitation conditions. However, all these studies have been conducted on European population. There is a possibility of variation in the basic parameters of DSI across geographical and ethnic groups. Hence, the present study evaluated DSI in Indian population. One hundred twenty voluntary participants (60 males, 60 females) who had G(0) on the Grade, Roughness, Breathiness, Aesthenia, Strain (GRBAS) scale participated in the study (age range of 18-25 years, M=21.8, standard deviation=2.7). Maximum phonation time (MPT), frequency intensity, and jitter measurements were made using CSL 4500 (Kay Elemetrics, Pine Brook, NJ). Results showed noticeable difference between Indian and European population on MPT, Highest frequency (F(0)-High), and DSI values. Significant gender difference was also observed on MPT and F(0)-High. Test-retest reliability showed >95% for all the parameters. The MPT decrement lead to a reduction in the overall DSI value in both the genders. These results of the study caution voice professionals to reinvestigate and establish their own norms for their geographical and ethnic groups.