Background: Several countries have recently changed their model of consent for organ donation from opt-in to opt-out. We undertook a systematic review to determine public knowledge and attitudes towards these models in Europe.
Methods: Six databases were explored between 1 January 2008 and 15 December 2017. We selected empirical studies addressing either knowledge or attitudes towards the systems of consent for deceased organ donation by lay people in Europe, including students. Study selection, data extraction, and quality assessment were conducted by two or more reviewers independently.
Findings: Awareness of the consent model was lower in opt-out countries than in opt-in countries. A majority of the public agrees with opt-in, regardless of the law in their own country. There are ambivalent attitudes regarding the opt-out system. The public tend to prefer opt-in and mandatory choice over opt-out when several options are offered.
Interpretation: The assumption that people in opt-out countries are aware of the legal requirements to be excluded from the pool of potential donors is not supported by the results of this review. This is a concern, since ignorance hinders people's autonomy regarding organ donation decision-making. Higher awareness of consent model in opt-in countries may reflect greater efforts to inform the public through campaigns to motivate donation. Legal moves towards opt-out are at odds with people's expressed preferences. Main limitations of this review are the lack of data from some countries, study population heterogeneity, and methodological shortcomings.