RESUMO
BACKGROUND: The Activity Scale for Kids (ASK) assesses the physical disability of children (5 to 15 years old) with neurological, orthopaedic or rheumatic diseases. The objective of this study was to translate and cross-culturally adapt the ASK for Brazilian Portuguese and assess the validity and reliability of the instrument. METHODS: A total of 67 children and adolescents with musculoskeletal, neurological or rheumatic diseases participated in the study. We evaluated the comprehension of the pre-final version of the questionnaire in 24 participants and reliability and validity in the other 43 participants. The translation and adaptation of ASK to Brazilian Portuguese followed guidelines from previous studies. The validity of the Brazilian Portuguese version of the ASK was verified through Spearman's correlation with the Pediatric Quality of Life Inventory™ Version 4.0 (PedQL). Intraclass correlation coefficient verified inter- and intra-evaluator reliability, while internal consistency was assessed using Cronbach's alpha. Scores were used to assess the standard error of the mean and minimal detectable change. RESULTS: The Brazilian Portuguese version of the ASK presented excellent reliability, internal consistency, agreement and moderate correlation with PedsQL (0.522, P < 0.001) between ASK performance and PedsQL; 0.537, P < 0.001 between ASK capacity and PedsQL. CONCLUSION: The Brazilian Portuguese version of the ASK has good validity and reliability and may be used by professionals and researchers to assess the functioning of children and adolescents with disabilities.