Glottal Function Index: Adaptation, Validity, and Reliability of the Turkish Version.

UNLABELLED

The aim of this study is to adapt the Glottal Function Index (GFI) into Turkish and to evaluate its validity and reliability.

METHOD

The scale was initially translated into Turkish by two Speech and Language Pathologists (SLP) and one ear, nose, and throat specialist, and then independently translated back into English by two different SLPs. The translations were compared by an expert proficient in both English and Turkish. The study included a total of 161 participants, with 91 having voice disorders and 70 not having voice disorders. All the participants in the study filled out the Voice Handicap Index (VHI), GFI. Additionally, auditory perceptual evaluation of voice was conducted on participants without voice disorders using the Grade, Roughness, Breathiness, Asthenia, Strain scale by a SLP. For the calculation of the test-retest reliability coefficient, the GFI was conducted again to a total of 64 participants, including 24 with voice disorders and 40 without voice disorders, at intervals of 7-14days. The internal consistency of GFI was examined using Cronbach's alpha coefficient.

RESULTS

The Turkish version of the GFI (GFI-TR) high internal consistency (Cronbach's alpha=0.932). The total GFI scores obtained from the two administrations of the test-retest reliability were examined. It was found that there was a high degree of correlation between the scores obtained in the two administrations (rho=0.972, P < 0.001). The construct validity of the GFI-TR was evaluated by examining the correlation with the VHI. It was observed that there was a high degree of correlation between GFI and VHI (rho=0.844, P < 0.001). Our hypothesis that there would be a statistically significant difference in GFI scores between participants with and without voice disorders has been confirmed. A statistically significant difference in GFI scores between the two groups was observed (U=59.000, z = -10.765, P < 0.001). This supports the Discriminative validity of the GFI-TR.

CONCLUSIONS

In conclusion, we believe that the GFI-TR, a brief and easily completed self-assessment tool, is a valid and reliable instrument. We recommend its use as part of the assessment process for voice disorders.