Objectives: Tinnitus is a phantom sound sensation without an external sound source. Due to its subjective and multifaceted nature it is measured using multi-item self-reported instruments. Many well-validated tinnitus-related questionnaires are available for clinical practice and scientific research, but so far no attention has been paid to their measurement invariance. The study aimed to examine measurement invariance of the Tinnitus Handicap Inventory with regard to gender and hearing impairment, and to identify the items that show differential item functioning (DIF) across the groups.
Design: This is a retrospective study using medical data from patients with tinnitus. They completed the Tinnitus Handicap Inventory (THI) and underwent pure-tone audiometry.
Study sample: 1106 adult patients with tinnitus (554 women and 552 men; 320 with normal hearing and 786 with hearing loss), aged 19-84 years.
Results: In the analysis, multi-group confirmatory factor analysis, hybrid ordinal logistic regression, Kernel smoothing in Item Response Theory, and lasso regression were applied. Measurement invariance was demonstrated across gender, but across hearing status the measurement was non-invariant. Five items were found to have DIF.
Conclusions: Researchers and clinicians should be aware of the potential risk of response bias when tinnitus severity is evaluated.
Keywords: Tinnitus; differential item functioning; measurement invariance; questionnaires.