RESUMEN
Background: Causality assessment of adverse drug reactions (ADRs) is an essential approach in pharmacovigilance. The World Health Organization-Uppsala Monitoring Center (WHO-UMC) system has been considered one of the most adequate method for establishing causal relationship in hospitalized patients. Objective: To describe the causality of potential ADRs in hospitalized patients assessed by the WHO-UMC system and by different healthcare professionals. Methods: Three healthcare professionals, with different backgrounds, acted as judges to adjudicate the causality categories for potential ADRs according to WHO-UMC system, in a Brazilian high complexity hospital. Judges' agreement was evaluated by using Fleiss' and Cohen's kappa coefficients. Results: Ninety potential ADRs identified in 300 participants were adjudicated by each judge, comprising a total of 270 assessments. Most potential ADRs were classified as probable or possible (77.8%). Fleiss´ kappa revealed slight concordance among judges (k = 0.096;CI:95%;0.01-0.18). Conclusions: Diverse backgrounds may have influenced the results for causality assessment of ADRs by employing the WHO-UMC system. Despite the slight concordance found for the method, this result suggests potential opportunity to enrich the ADRs management by engaging multiprofessional teams in the process. Further studies should be considered to investigate the performance of methods for ADRs assessment in hospitalized patients in low- and middle-income countries.