Background Children are more vulnerable to adverse drug reactions (ADRs) due to complex changes in the body during the growth process and lack specific pharmacoepidemiologic studies. Causality and Avoidability assessment of ADRs are relevant to clinical guidelines development and pharmacovigilance. This study aimed to translate and transcultural adapt two new tools—Liverpool Causality Assessment Tool (LCAT) and the Liverpool Avoidability Assessment Tool (LAAT)—to Brazilian-Portuguese and evaluate the psychometric properties of these tools to analyse ADRs in Brazilian children. Methods The validation of the cross-cultural adaptation of tools was obtained by the functional (conceptual, semantic, operational, and measurement) equivalence between the original and translated versions of each instrument. The translated version of LCAT and LAAT was applied to assessing the twenty-six case reports of suspected adverse drug reactions in a Brazilian teaching paediatric hospital. The inter-rater reliability (a pharmacist and a physician) was evaluated using Cronbach’s alpha. The exact agreement percentages (%EA) and extreme disagreement (%ED) were computed. Overall Kappa index was calculated with a 95% confidence interval. Results There was a need to modify some terms translated into Portuguese for semantic and conceptual equivalence. The Cronbach’s alpha coefficient values obtained were 0.95 and 0.85, and the weighted Kappa (95% confidence interval) were 0.82 (0.67–0.97) and 0.68 (0.45–0.91) for LCAT and LAAT, respectively. The Brazilian-Portuguese versions of the LCAT and LAAT showed reliable and valid tools for the diagnosis and follow-up of ADRs in children. Conclusion The methodological approach allowed the translation, transcultural adaptation, and validation to Brazilian-Portuguese of two easy and quick to perform tools for causality and avoidability of ADRs in children by a multidisciplinary expert specialist committee, including the authors of original tools. We believe these versions may be applied by professionals (patient safety teams) and researchers in Brazil in groups or by a single reviewer. Trial registration This study was evaluated and approved by the Research Ethics Committee (Instituto de Pediatria e Puericultura Martagão Gesteira – Federal University of Rio de Janeiro – Number: 3.264.238.

Background: Children are more vulnerable to adverse drug reactions (ADRs) due to complex changes in the body during the growth process and lack specific pharmacoepidemiologic studies. Causality and Avoidability assessment of ADRs are relevant to clinical guidelines development and pharmacovigilance. This study aimed to translate and cross-culturally adapt two new tools - Liverpool Causality Assessment Tool (LCAT) and the Liverpool Avoidability Assessment Tool (LAAT) - to Brazilian-Portuguese and evaluate the psychometric properties of these tools to analyze ADRs in Brazilian children.Methods: The validation of the cross-cultural adaptation of tools was obtained by the functional equivalence (degree of agreement between conceptual and item equivalence, semantic equivalence, operational and measurement equivalence) between the original versions two translated versions of each tool. The second version of LCAT and LAAT was applied to assessing the twenty-six case reports of suspected adverse drug reactions in a Brazilian teaching pediatric hospital. The inter-rater reliability (a pharmacist and a physician) was evaluated using Cronbach's alpha. The exact agreement percentages (%EA) and extreme disagreement (%ED) were computed. Overall Kappa index was calculated with a 95% confidence interval. Results: Some words and terms needed carefully discussed and examined to improve the clarity of the Portuguese language tools. The Cronbach's alpha coefficient values obtained were 0.95 and 0.85, and the weighted Kappa (95% confidence interval) were 0.82 (0.67-0.97) and 0.68 (0.45-0.91) for LCAT and LAAT, respectively. The Brazilian-Portuguese versions of the LCAT and LAAT showed reliable and valid tools for the diagnosis and follow-up of ADRs in children. Conclusion: The methodological approach allowed the translation, transcultural adaptation, and validation to Brazilian-Portuguese of two easy and quick to perform tools for causality and avoidability of ADRs in children by a multidisciplinary expert specialist committee, including the authors of original tools. We believe this version may be applied by professionals (patient safety teams) and researchers in Brazil in groups or by a single reviewer.Trial registration: This study was evaluated and approved by the Research Ethics Committee (Instituto de Pediatria e Puericultura Martagão Gesteira – Federal University of Rio de Janeiro – Number: 3.264.238.