Translation, cross-cultural adaptation and factor analysis of the Persian version of ankle instability instrument

Background: Ankle Instability Instrument (AII) is a questionnaire for determination of ankle stability status. The aim of this study is to cross-culturally translate and investigate the reliability and validity of AII in a sample of Persian-speaking Iranians, suffering from ankle sprain. Methods: One hundred twenty persons with a history of ankle sprain were recruited in the study. All participants completed the Persian version of Ankle Instability Instrument, Cumberland Ankle Instability Tool (CAIT), Foot and Ankle Ability Measure (FAAM) and Foot and Ankle Outcome Score (FAOS) at the baseline. Out of them, 60 randomly selected subjects completed the questionnaires once more, one week later. Face validity, Test-retest reliability, internal consistency, standard error of measurement, minimal metric detectable change, spearman's correlation coefficient and confirmatory factor analysis of AII measured. We used Lisrel v 8.80 software with significant level of p<0.05. Results: Persian version of AII is clear and unambiguous and its qualitative face validity was confirmed in the pilot study on the 20 subjects with a lateral ankle sprain. The interclass correlation coefficient, Cronbach's alpha, standard error of measurement and minimal metric detectable change were 0.93, 0.87, 0.81 and 2.25 (95% confidence interval, 0.85-0.96). The Spearman correlations coefficients between AII, and CAIT, FAAM and FAOS measures were 0.91, 0.71 and 0.69 respectively. The original three factor structure of AII was replicated based on the confirmatory factor analysis. Which showed an adequate fit of the model to the data and goodness-of-various fit indices. Conclusion: The Ankle Instability Instrument Persian Version (AII-PV) is a reliable and valid measure for assessing the ankle stability status.