Transparency in the secondary use of health data: assessing the status quo of guidance and best practices.

We evaluated what guidance exists in the literature to improve the transparency of studies that make secondary use of health data. To find peer-reviewed papers, we searched PubMed and Google Scholar. To find institutional documents, we used our personal expertise to draft a list of health organizations and searched their websites. We quantitatively and qualitatively coded different types of research transparency: registration, methods reporting, results reporting, data sharing and code sharing. We found 56 documents that provide recommendations to improve the transparency of studies making secondary use of health data, mainly in relation to study registration ( = 27) and/or methods reporting ( = 39). Only three documents made recommendations on data sharing or code sharing. Recommendations for study registration and methods reporting mainly came in the form of structured documents like registration templates and reporting guidelines. Aside from the recommendations aimed directly at researchers, we also found recommendations aimed at the wider research community, typically on how to improve research infrastructure. Limitations or challenges of improving transparency were rarely mentioned, highlighting the need for more nuance in providing transparency guidance for studies that make secondary use of health data.