Validation of the psychometric properties of the FIATS-AAC-Br: internal consistency reliability, test-retest reliability and convergent validity

The Family Impact of Assistive Technology Scale for Augmentative and Alternative Communication (FIATS-AAC) was developed to assess the impact of AAC systems on children and adolescents with complex communication needs based on family reports. A first study was conducted regarding the theoretical validation process of the scale, including initial translation, reconciled translation, content validity by experts, back-translation, and face validity. This article describes the steps taken for the preliminary validation of the psychometric properties of the cross-culturally adapted version of the scale into Brazilian Portuguese, the FIATS-AAC-Br. For the research development, FIATS-AAC-Br, the Participant Characterization Questionnaire developed for the research, and the Pediatric Quality of Life Inventory (PedsQL^™) - Family Impact Module were used to assess the convergent validity of the scale as a comparative measure. Reliability analysis, including assessment of internal consistency and scale stability, was performed with 30 participants who completed both the Participant Characterization Questionnaire and the FIATS-AAC-Br. Cronbach's alpha calculation indicated excellent internal consistency from scale total (α = 0.94). The Intraclass Correlation Coefficient (ICC) demonstrated high stability for both the total FIATS-AAC-Br (ICC = 0.96; 95% CI = 0.92-0.98) and its 13 dimensions. Convergent validity was assessed with Pearson's Correlation Coefficient between the FIATS-AAC-Br and the PedsQL^™, demonstrating a significant positive correlation (Pearson <i>r</i> = 0.719, <i>p</i> < 0.001). These results contribute to establishing a measuring tool for professionals and services working with AAC in monitoring proposed interventions.