Introduction
The causality assessment of adverse drug reactions (ADR) is an essential approach in pharmacovigilance, as an attempt to investigate the connection between the use of a drug and a suspected ADR. WHO-UMC system is a universally used method for causality assessment.[1] Previous data emphasized its high consistency to be applied in hospitalized patients. However, there are some limitations raised by some authors regarding the fact that it is based on individual knowledge and judgment, and a poor reproducibility has been encountered among different judges.[1, 2] Naranjo algorithm is another method used to assess ADR causality which has been reported to be simple and brief. This is widely used due to its easy implementation and high interrater agreement, despite poor sensitivity.[1-4]
Causality assessment presupposes theoretical-methodological integration, but requires judgments which are essential for drug safety evaluation.[4] Adequate categorization of causality, especially in highly complex institutions, may contribute to the early recognition of ADR and their consequent prevention, in addition to the optimization of drug therapy.[3] We sought to assess causality of ADR in patients hospitalized in a university hospital, using the WHO-UMC method, to evaluate the performance of Naranjo algorithm[5] and ADR preventability using an adapted Schumock and Thornton method.[6, 7]