Glottal Function Index: Validity and Reliability of the Persian Language Version in Patients With Voice Disorders

Author links open overlay panelHadi Torabi *, NoureddinNakhostin Ansari ^†, Farzad Zamani ^‡, Hamid Dalvand

Abstract

Objective: To translate and cross-culturally adapt the Glottal Function Index into the Persian language (GFIp) and validate it in patients with voice disorders.

Study design:A cross-sectional and prospective validation design was adopted.

Method:The GFI was translated and culturally adapted into Persian language according to the methodology of standard forward-backward translations to obtain semantic, idiomatic, and conceptual equivalence. One hundred patients with voice disorders (53 men; mean age: 41.4 ± 13.6 years) and 40 healthy volunteers (21 women; mean age: 36.7 ± 10.0 years) completed the GFIp. Patients with voice disorders also completed the Persian Voice Handicap Index (VHIp) to assess the construct validity.

Results:There were no floor and ceiling effects. Evidence for construct validity was found with a significant very good correlation between the GFIp and the VHIp total scores (r = 0.70; P < 0.001). Differences of GFIp scores between the patients and healthy participants were statistically significant (P < 0.001) confirming discriminant validity. The internal consistency reliability was acceptable for GFIp (Cronbach's α = 0.74). Absolute reliability measures of Standard Error of Measurement and the Smallest Detectable Change for GFIp were 2.5 (confidence interval 95% = ±4.9) and 6.93, respectively. Factor analysis revealed the GFIp as a single factor instrument.

Conclusion:The GFIp is a valid and reliable self-administered instrument for use in Persian-speaking patients with voice disorders.

Accepted 19 October 2020, Available online 26 November 2020, Version of Record 4 January 2023.

Volume 37, Issue 1, January 2023, Pages 140.e1-140.e6

https://doi.org/10.1016/j.jvoice.2020.10.013