Psychometric Validity, Reliability, and Responsiveness of the Tinnitus Functional Index

The effects of treatments on tinnitus have been difficult to quantify. The Tinnitus Functional Index (TFI) has been proposed as a standard questionnaire for measurement of tinnitus treatment outcomes. For a questionnaire to achieve wide acceptance, its psychometric properties need to be confirmed in different populations.

To determine if the TFI is a reliable and valid measure of tinnitus, and if its psychometric properties are suitable for use as an outcome measure.

A psychometric evaluation of the TFI from secondary data obtained from a cross-sectional clinic survey and a clinical trial undertaken in New Zealand.

Confirmatory factor analysis and evaluation of internal consistency reliability were undertaken on a sample of 318 patients with the primary complaint of tinnitus. In a separate sample of 40 research volunteers, test-retest reliability, convergent and divergent validity were evaluated. Both samples consisted of predominantly older Caucasian male patients with tinnitus.

The internal structure of the original US TFI was confirmed. The Cronbach's Alpha and Intraclass correlation coefficients were >0.7 for the TFI overall and each of its subscales, indicating high internal consistency and test-retest reliability. Strong Pearson correlations with the Tinnitus Handicap Questionnaire and tinnitus numerical rating scales indicated excellent convergent validity, and a moderate correlation with the Hearing Handicap Inventory, indicated moderate divergent validity. Evaluation of the clinical trial showed good test-retest reliability and agreement between no-treatment baselines with a smallest detectable change of 4.8 points.

The TFI is a reliable and valid measure of tinnitus severity in the population tested and is responsive to treatment-related change. Further research as to the TFI's responsiveness to treatment is needed across different populations.