Functional and social limitations after facial palsy: expanded and independent validation of the Italian version of the facial disability index

The Facial Disability Index (FDI) is widely used for self-assessment of functional impairment and quality of life in patients with facial palsy. The study aim was to complete the validation of the FDI by generating an Italian version (IT-FDI) and evaluating its clinimetric properties. This was a longitudinal, observational measurement study. The questionnaire was translated, cross-culturally adapted, and administered to 100 consecutive participants (outpatients) with facial palsy. The clinical severity of facial palsy, impairments in physical and social function, and quality of life were evaluated with the Sunnybrook Facial Grading System, IT-FDI, and 12-Item Short-Form Health Survey. The IT-FDI showed excellent test-retest reliability for every item and for total scores (intraclass correlation coefficients of .93 and .84 for physical function subscale and social/well-being function subscale, respectively). The IT-FDI confirmed the high internal consistency of the original version, with theta coefficients of .82 for the physical function subscale and .78 for the social/well-being function subscale. The physical function subscale correlated with the Sunnybrook Facial Grading System composite score (r=.44), and the social/well-being function subscale correlated with the 12-Item Short-Form Health Survey mental component (r=.55). The IT-FDI confirmed the good responsiveness of the original version, as expressed by effect size, standardized response mean, and responsiveness ratio of, respectively, 1, 1.03, and 1.21 for the physical function subscale and 0.75, 0.83, and 1.15 for the social/well-being function subscale. Responsiveness was evaluated with a limited number of participants. The results demonstrated the test-retest reliability for all items of the FDI and confirmed its internal consistency, construct validity, and responsiveness with an independent and larger clinical subset. This study completes the validation of the FDI and provides the first validated questionnaire in Italian for assessment of disability and quality of life specifically in patients with facial palsy.