Background: The aims of this study were to adapt the Identification of Functional Ankle Instability (IdFAI) questionnaire into a simplified Chinese version and to assess its reliability, validity, and responsiveness in Chinese-speaking patients with chronic ankle instability (CAI) disorders.
Methods: The simplified Chinese version of the IdFAI (SC-IdFAI) questionnaire was developed with a five-step procedure involving cross-cultural translation and adaptation. Three questionnaires, including the SC-IdFAI, Medical Outcomes Study Short-Form 36 (SF-36), and Foot and Ankle Ability Measure (FAAM), were administered to the recruited patients. Then, the Cronbach's alpha value, intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC), Spearman's correlation coefficient (rs), effect size (ES), and standardized response mean (SRM) were calculated to evaluate the reliability, validity, and responsiveness of the SC-IdFAI questionnaire.
Results: A total of 131, 119, and 86 patients with CAI successfully completed the first, second, and third rounds of the questionnaires, respectively. Good or excellent internal consistency and test-retest reliability were found for the overall scale and subscales of the SC-IdFAI questionnaire. The values for the SEM (1.346) and MDC (3.73) were low, indicating that small clinical changes can be detected by the SC-IdFAI questionnaire. The correlations of the SC-IdFAI with FAAM and SF-36 were generally in agreement with the a priori hypotheses (85%, 34/40), suggesting the SC-IdFAI questionnaire has good construct validity. Moreover, the results suggest that the SC-IdFAI (ES = 1.123 and SRM = 1.554) has an acceptable level of responsiveness.
Conclusion: The SC-IdFAI scale may be an effective tool, and it is responsive, reliable and valid for the assessment of Chinese patients suffering from CAI.
Keywords: Cross-culture translation; IdFAI; Psychometrics; Validation.