Validity and reliability of the Glottal Function Index

Kevin K. Bach, Peter C Belafsky, Kathleen Wasylik, Gregory N. Postma, Jamie A. Koufman

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

Objective: To evaluate a symptom-focused vocal impairment instrument for the evaluation of patients with voice disorders. Design: Prospective, nonrandomized study of patients with voice disorders undergoing treatment with validation of a new symptom index, the Glottal Function Index (GFI). Setting: Voice disorders clinic at an academic tertiary care hospital. Patients: Consecutive patients undergoing therapy for glottal insufficiency, adductor spasmodic dysphonia, nodules, and granuloma (40 patients in each group) and 40 control patients. Interventions: The Pearson correlation coefficient was used to evaluate GFI reproducibility and to compare it with the Voice Handicap Index (VHI). The paired-samples t test was used to compare pretherapy and posttherapy GFI values. Main Outcome Measures: Correlation of GFI with VHI; comparison of the GFI in normals, and in pretherapy and posttherapy GFI and VHI scores. Results: The mean ± SD normative GFI score was 0.87±1.32. The correlation coefficient for GFI between independent pretherapy measurements was 0.56 (P<.001). The correlation coefficient between total GFI and total VHI scores was 0.61 (P<.001). The mean posttherapy GFI scores improved among all groups as follows: glottal insufficiency: presenting GFI score, 12.7±4.1; posttherapy GFI score, 6.8±5.4; nodules: presenting GFI score, 12.9±4.2; posttherapy GFI score, 8.9±4.6; adductor spasmodic dysphonia: presenting GFI score, 13.2±4.1; posttherapy GFI score, 8.9± 4.9; and granuloma: presenting GFI score, 7.8±4.6; posttherapy GFI score, 3.8±2.1. Relative to controls, the GFI score at presentation was significantly elevated and demonstrated significant reduction following treatment across each of these entities (P<.05). Conclusions: The GFI is a reliable, reproducible, 4-item, self-administered symptom index with excellent criterion-based and construct validity. Its advantages over existing indexes include brevity and ease of administration. The GFI is a useful adjunct in the evaluation and treatment of patients with glottal dysfunction.

Original languageEnglish (US)
Pages (from-to)961-964
Number of pages4
JournalArchives of Otolaryngology - Head and Neck Surgery
Volume131
Issue number11
DOIs
StatePublished - Nov 2005

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Reproducibility of Results
Voice Disorders
Dysphonia
Granuloma
Tertiary Healthcare
Therapeutics
Tertiary Care Centers
Outcome Assessment (Health Care)
Prospective Studies
Control Groups

ASJC Scopus subject areas

  • Otorhinolaryngology

Cite this

Validity and reliability of the Glottal Function Index. / Bach, Kevin K.; Belafsky, Peter C; Wasylik, Kathleen; Postma, Gregory N.; Koufman, Jamie A.

In: Archives of Otolaryngology - Head and Neck Surgery, Vol. 131, No. 11, 11.2005, p. 961-964.

Research output: Contribution to journalArticle

Bach, Kevin K. ; Belafsky, Peter C ; Wasylik, Kathleen ; Postma, Gregory N. ; Koufman, Jamie A. / Validity and reliability of the Glottal Function Index. In: Archives of Otolaryngology - Head and Neck Surgery. 2005 ; Vol. 131, No. 11. pp. 961-964.
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AU - Postma, Gregory N.

AU - Koufman, Jamie A.

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N2 - Objective: To evaluate a symptom-focused vocal impairment instrument for the evaluation of patients with voice disorders. Design: Prospective, nonrandomized study of patients with voice disorders undergoing treatment with validation of a new symptom index, the Glottal Function Index (GFI). Setting: Voice disorders clinic at an academic tertiary care hospital. Patients: Consecutive patients undergoing therapy for glottal insufficiency, adductor spasmodic dysphonia, nodules, and granuloma (40 patients in each group) and 40 control patients. Interventions: The Pearson correlation coefficient was used to evaluate GFI reproducibility and to compare it with the Voice Handicap Index (VHI). The paired-samples t test was used to compare pretherapy and posttherapy GFI values. Main Outcome Measures: Correlation of GFI with VHI; comparison of the GFI in normals, and in pretherapy and posttherapy GFI and VHI scores. Results: The mean ± SD normative GFI score was 0.87±1.32. The correlation coefficient for GFI between independent pretherapy measurements was 0.56 (P<.001). The correlation coefficient between total GFI and total VHI scores was 0.61 (P<.001). The mean posttherapy GFI scores improved among all groups as follows: glottal insufficiency: presenting GFI score, 12.7±4.1; posttherapy GFI score, 6.8±5.4; nodules: presenting GFI score, 12.9±4.2; posttherapy GFI score, 8.9±4.6; adductor spasmodic dysphonia: presenting GFI score, 13.2±4.1; posttherapy GFI score, 8.9± 4.9; and granuloma: presenting GFI score, 7.8±4.6; posttherapy GFI score, 3.8±2.1. Relative to controls, the GFI score at presentation was significantly elevated and demonstrated significant reduction following treatment across each of these entities (P<.05). Conclusions: The GFI is a reliable, reproducible, 4-item, self-administered symptom index with excellent criterion-based and construct validity. Its advantages over existing indexes include brevity and ease of administration. The GFI is a useful adjunct in the evaluation and treatment of patients with glottal dysfunction.

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