Background As routinely collected patient data have become increasingly accessible over the years, more and more attention has been directed at the ethics of using such data for research purposes. Patient data is often available to researchers through patient registries that typically collect data of patients with a specific disease. While ethical guidelines for using patient data are presented frequently in research papers and institutional documents, it is currently unknown how patient registries implement the recommendations from these guidelines in practice and how they communicate their practices. In this project, we assessed to what extent a sample of 51 patient registries provides information about a range of ethics practices. Methods We searched for patient registries in the resource database of the European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (ENCePP). Our assessment checklist was based on three sources: REQueST, a tool for the assessment of registry quality, AHRQ's guide for good registry practices, and a systematic review of the principles and norms related to health data sharing by Kalkman and colleagues. The checklist includes 26 questions about five ethics components: governance, conflicts of interest, informed consent, privacy, and use-and-access. Results We found substantial heterogeneity in the way patient registries provide information about ethics practices: some registries rarely provide information; others discuss all relevant practices and more. Patient registries often mentioned their governance structure and any potential conflicts of interests but typically did not describe the responsibilities and rights allocated to their funders. Information about informed consent was often provided to patients but the available documents often lacked relevant information like the benefits and risks of participation. Privacy and use-and-access policies were typically discussed but not very concrete. Conclusions We can conclude that registries typically provide information about key ethics practices such as governance, conflicts of interest, informed consent, privacy, and use-and-access procedures, but that this information is often not as detailed as recommended in existing guidelines. The checklist we designed for our assessment could be helpful for the ethical assessments of patient registries and other types of registries in the future, as well as for self-assessment of registries that aim to improve their ethics practices.

The authors have declared no competing interest.

We have received funding from the European Union's Horizon Europe Research and Innovation Actions under grant no. 101095479 (More-EUROPA). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union nor the granting authority. Neither the European Union nor the granting authority can be held responsible for them.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes