Translation, cross-cultural adaptation and validation of psychometric properties of foot function index in Urdu-speaking population with ankle and foot disorders

Abstract

Background: Foot and ankle problems are frequently prevalent, especially among the elderly, ranging from 70 to 80%. In primary care, foot, and ankle complaints stand out as one of the most frequent reasons for orthopedic consultations. Patient-reported outcome measures are significant in the assessment burden of any condition on the effects of intervention as well as research. The Foot Function Index (FFI) is a region-specific tool that was identified as one of the most commonly used evaluation tools for foot complaints. This study aimed to translate, cross-cultural adapt, and test the psychometric properties of FFI in the Urdu language. Methodology: The FFI was translated into Urdu language (FFI-U) following Beaton et al. translation guidelines. The data were collected from 230 Urdu-speaking participants with different foot and ankle pathologies. Data collection started after the written informed consent from the participants. All participants completed the FFI-U, Visual Analogue Scale (VAS), SF-36, and the Foot and Ankle Outcome Score (FAOS) at baseline while only 30 participants completed ULFI-U after one week for test-retest reliability. The psychometric properties involved reliability and validity testing. Reliability was assessed where internal consistency was measured using Cronbach’s alpha and test-retest reliability through the intra-class correlation coefficient (ICC). FFI-U was tested for face validity and construct validity (convergent and discriminant). Psychometric criteria were examined against priori hypotheses, and alpha level (p-value < 0.05) was considered statistically significant. Results: FFI-U demonstrated good reliability with internal consistency (α = 0.86) and test-retest reliability with intra-class correlation coefficient = 0.845 (0.78–0.89). A moderate correlation was found using Pearson correlation between FFI-U total score and physical components of SF-36, VAS (pain, disability), and FAOS (γ= -0.65, 0.72, 0.71, -0.68) respectively, indicating convergent validity however, a weak correlation was found with mental components of SF-36 (γ=-0.25) demonstrating discriminant validity. Face validity was assessed at the pre-final testing stage by interviewing patients. There were no floor and ceiling effects found for FFI-U. Conclusion: The FFI-U has been found reliable, valid, and feasible tool to be used as a patient-reported outcome measure to assess functional levels with different foot and ankle disorders in Urdu speaking population.