Translation, cross-cultural adaptation, reliability, and validity of the Identification of Functional Ankle Instability questionnaire in Persian speaking participants with a history of ankle sprain

Purpose: To cross-culturally translate the Identification of Functional Ankle Instability (IdFAI) questionnaire into Persian and to assess its psychometric properties and factor structure. Methods: The Persian version of IdFAI questionnaire was prepared after a forward-backward translation and cultural adaptation process. One hundred and twenty patients with a history of lateral ankle sprain completed the Persian version of this questionnaire and the Cumberland Ankle Instability Tool (CAIT), Foot and Ankle Ability Measure, Foot and Ankle Outcome Score, Fear Avoidance Belief questionnaire and the Tampa Scale of Kinesiophobia in the first test session. Afterwards, 60 randomly selected patients completed the questionnaires in the second session. Psychometric testing which included test-retest reliability, internal consistency, standard error of measurement (SEM) and minimal metric detectable change (MMDC), weighted kappa coefficient and construct validity were performed using Spearman's correlation coefficient and confirmatory factor analysis of the three-factor structure of the IdFAI. Results: The interclass correlation coefficient, Cronbach's alpha, SEM and MMDC were 0.91, 0.95, 2.43, and 6.73 (95% confidence interval, 0.86-0.95) for the IdFAI, respectively. The repeatability of all the questions after one week was rated good to excellent (kappa = 0.60-0.93, p < 0.001). The IdFAI total score had strong correlation with CAIT measure, but had moderate correlation with other questionnaires. The results of factor analysis showed an adequate fit of the model to the data and goodness-of-various fit indices. Conclusions: The Persian version of IdFAI is a reliable and valid tool to identify patients with functional ankle instability which have a history of ankle sprain. Its original three-factor structure was replicated in this study.