Validity and reliability of instruments for global measurement of disability: Systematic literature review

Introduction: Various theoretical and conceptual frameworks have historically shaped the measurement of disability, many focusing on activity limitations due to impairments in bodily functions or structures. However, these perspectives do not comprehensively address other components, such as environmental factors and participation in life situations under various health conditions, which would provide a more holistic measurement of global disability. Objective: This study aimed to provide a comprehensive overview of the available instruments for assessing disability using the ICF model. Additionally, the study sought to examine the validity and reliability of assessment procedures applied to these instruments. Methodology: A systematic literature review was conducted following PRISMA guidelines. Searches were performed in Ovid, Embase, LILACS, Scopus, Rehabilitation Reference Center, and Google Scholar from 2012 to 2022. Independent reviewers performed screening, selection, and data extraction. Risk of bias assessment according to COSMIN and GRADE level of evidence was applied. Results: A total of 1,998 articles were identified, 188 were reviewed in full text, and 3 were included in the review. The identified scales for assessing global disability were WHODAS 2.0 and IMPACT-S. The quality of measurement properties for the first scale was indeterminate for structural validity and internal consistency and sufficient for hypothesis testing; the level of evidence was moderate. The IMPACT-S was indeterminate for structural validity and sufficient for internal consistency, reliability, criterion validity, and hypothesis testing. Conclusions: The most widely used instrument for measuring global disability is WHODAS 2.0, which has proven preventable across different contexts and populations.