Opt-In versus opt-out for the secondary use of routinely recorded health data: A randomized controlled trial

Importance: Optimal data availability for secondary use is crucial for continuous improvement in healthcare. At the same time, it is imperative to uphold patients’ rights to be informed, to control the use of their health data and to protect their privacy. To balance these two needs, we investigated which consent procedure (opt-in or opt-out) would be most supportive of data availability. Objective: This study explores an opt-in procedure versus an opt-out procedure as a consent procurement method for secondary use of routinely recorded health data, images and tissues for scientific research purposes. Design/Setting: A randomized controlled trial was performed in Erasmus Medical Center, a large tertiary hospital in the Netherlands. New, first time patients were recruited from 16 outpatient clinics and randomily assigned to either the opt-in (intervention group) or the opt-out procedure (control group), until the equally balanced sample size of 2228 was reached. Results: Patient inclusion spanned from December 2022 to September 2023. The opt-out procedure resulted in higher consent rates compared to the opt-in procedure. Differences were found for gender, socioeconomic status and country of birth. Conclusions: An opt-out procedure appears to be more effective in ensuring optimal data availability with less bias for the secondary use of health data compared to opt-in. To uphold patient control over data, it is pivotal that patients are well-informed about the consent procedure.