Validation of the Lithuanian Version of the Glottal Function Index

SummaryObjectiveTo culturally adapt the Glottal Function Index (GFI) questionnaire to the Lithuanian language, and to validate it.MethodsPsychometric analyses were performed on the translated Lithuanian version of the GFI (GFI-LT) as described by the Scientific Advisory Committee of the Medical Outcomes Trust. The GFI-LT was completed by 50 voice-disordered individuals and by 50 healthy subjects of the control group. Validity, reliability, reproducibility, sensitivity, and responsiveness to clinical change of the GFI-LT were evaluated. To assess the concurrent validity of the GFI-LT, all participants also completed the Voice Handicap Index (VHI) questionnaire.ResultsThe GFI-LT showed a statistically significantly high reliability and internal consistency (Cronbach α = 0.8, r = 0.50), and moderate item-total correlation (r = 0.41–0.55). Cronbach α coefficients of the test-retest reliability were above the standard (≥0.9) for individuals testing. There was a statistically significant difference between the mean scores of the control and the voice-disordered groups (P < 0.001). The Receiver Operating Characteristic test indicated that the GFI-LT score of >3.0 was the optimal score distinguishing patients and healthy controls with the sensitivity of 88% and specificity of 84%. Statistically significant (P < 0.05) strong correlations were found between the GFI-LT and VHI scores. The GFI-LT was found to be a responsive measurement instrument to patients’ clinical statement; mean difference of the GFI-LT scores in the group of voice-disordered patients before and after surgical treatment was 5.7 (P < 0.001).ConclusionThe GFI-LT is considered to be a valid and reliable tool for self-assessment of the severity of voice disorders in Lithuanian-speaking patients.