Translation, Validity, and Reliability of Singing Voice Handicap Index in Persian Traditional Singers: A New Revised Version

Background: The singing voice handicap index (SVHI) was developed to assess voice-related handicaps in singers. Objectives: The purpose of this study was to evaluate the validity and reliability of a Persian translation of the SVHI (P-SVHI) for traditional Persian singers. Methods: A cross-sectional study was performed to translate and validate the P-SVHI using a "forward-backward" procedure. The questionnaire was administered to 275 traditional Persian singers (168 with a normal voice and 107 with dysphonia) ranging from 16 to 83 years. Content, construct, discriminant, convergent, and face validity, test-retest reliability, internal consistency, and floor and ceiling effects were assessed. Results: The 36-item SVHI, translated from the original English by two translators, was completed by 21 traditional Persian singers. After the face validity was approved, construct validity assessment using factor analysis identified four factors in the P-SVHI with the exclusion of seven items. The mean score of the 29-item P-SVHI on a 0 - 100 scale was 16.9 for healthy subjects and 40.9 for dysphonic subjects. Discriminant validity confirmed that P-SVHI scores were significantly different between normal and dysphonic singers, using an independent sample t-test (P < 0.001). Convergent validity was proven by strong correlations between P-SVHI scores and the Iowa Patient’s Voice Index (IPVI1, IPVI2, and "IPVI effort" scores of r = 0.58, 0.69, and 0.42, respectively, P < 0.001). Internal consistency and test-retest reliability were also excellent (Cronbach α = 0.95, average inter-item correlation = 0.40, and intra-class correlation coefficients using two-way random model with absolute agreement, ICCtwo-way random, absolute agreement = 0.69 - 0.95). No floor or ceiling effects were observed. Conclusions: The revised 29-item P-SVHI is a valid and reliable tool in differentiating normal and dysphonic Persian traditional singers.