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



Torabi H¹ ; Ansari NN² ; Zamani F³ ; Dalvand H⁴
Source: Journal of Voice Published:2023

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. © 2020 The Voice Foundation