Revealing the Weakness of Evidence Regarding Presumed Consent Efficacy: A Systematic, Framework-guided Review of...

The effectiveness of presumed consent policies in increasing donation and transplantation rates remains a matter of debate within the transplant community. The rationale for their implementation was derived from a limited body of experimental evidence and has largely relied on cross-country panel analyses reporting higher donation rates in opt-out systems. However, no previous study has systematically examined the risk of bias inherent in these analyses using a structured methodological framework. To address this gap, an operative framework of the deceased donation process was developed through the systematization of its phases and conditioning factors. This framework was subsequently used to perform a systematic review of cross-country panel data studies, applying the Risk Of Bias In Nonrandomized Studies of Interventions tool to assess risk of bias. Eighteen studies were identified. Although most (n = 12) reported higher donation and/or transplantation rates in countries with presumed consent, risk of bias assessment identified serious limitations in 16 studies and critical limitations in 2. The principal concerns were inadequate control of confounding factors and misclassification bias resulting from imprecise definitions of how consent policies are implemented in practice, beyond the legal distinction between opt-in and opt-out systems. These findings suggest that, despite their apparent consistency, cross-country panel studies do not provide sufficiently robust evidence to support presumed consent as an effective strategy for increasing donation and transplantation rates. Greater emphasis should therefore be placed on the development of evidence-based donation policies that incorporate all validated determinants of effective deceased donation systems worldwide. Recommendations for improving research design in this field are also proposed.