Responsiveness of the Brazilian IdFAI questionnaire in patients with chronic ankle instability

Purpose This study aimed to determine the responsiveness of the Brazilian version of the Identification of Functional Ankle Instability (IdFAI) questionnaire in students who received an eight-week treatment for chronic ankle instability (CAI). Methods Twenty-five college students (aged 23.12 +/- 2.80 years) with CAI, as identified by the IdFAI questionnaire, were recruited. We used distribution and anchor-based methods to assess the responsiveness of the questionnaire, and its ability to determine clinical changes in participants. Eleven anchors were used: Visual Analog Scale for instability (VAS-i); Cumberland Ankle Instability Tool (CAIT); Isometric dorsiflexion, plantar flexion, inversion, and eversion muscle strength measured using a manual dynamometer; Dynamic balance as assessed through the Star Excursion Balance Test (SEBT-Y); Active ankle dorsiflexion range of motion as measured using the weight-bearing lunge test; and Functional performance assessment using three hop tests: single hop, triple crossover hop, and side hop. The distribution-based method used effect size (ES) and standardized response mean (SRM), whereas the anchor-based method used paired t-tests. Both methods allowed the calculation of the minimal important difference (MID). Results The Brazilian IdFAI showed high responsiveness, with a large magnitude of change (ES = 1.34) and a high responsiveness index (SRM = 1.28) when assessed after a treatment for CAI. The IdFAI total score (p < .001) and all the 11 anchors [VAS-i (p < .001); CAIT (p < .001); Isometric dorsiflexion (p < .001), plantar flexion (p < .001), inversion (p < .001), and eversion (p < .001) muscle strength; SEBT-Y (p < .001); Lunge test (p = .002); Single hop (p < .001); triple crossover hop (p < .001); and side hop tests (p < .001)] showed significant differences. The anchor and distribution-based methods demonstrated MID values of 3.72 and 1.49-2.27, respectively. Conclusion The Brazilian IdFAI questionnaire is a patient-reported outcome measure sensitive to clinical changes in individuals with CAI. It can be used as an identification of patients with CAI, and as a parameter to verify clinical changes of clinical trials or therapeutic interventions in the population with CAI.