With many peer-reviewed journals now insisting that study authors be prepared to share raw, unprocessed data with other scientists or declare the availability of raw data in published articles, there is more of a risk that patient confidentiality will be breached.

So far, though, there has been little advice on how these data should be prepared for distribution. New guidance published in the open-access journal Trials and on bmj.com addresses this issue with practical recommendations on anonymising or de-identifying data to ensure patient privacy when sharing clinical research.

Sir Ian Hrynaszkiewicz and colleagues say researchers should seek informed consent about data-sharing from clinical trial participants before studies begin. They list 28 items of personal and clinical information that can make patients identifiable in anonymised datasets and recommend that, unless patients have explicitly consented to data-sharing, all direct identifiers such as names should be removed.

If three or more indirect identifiers, such as age or sex, are provided on any patient, researchers should ask an independent expert or ethics committee to assess the risk of breaching confidentiality before sharing the data, Hrynaszkiewicz et al add.

They also advise authors to make explicit statements in research articles that link to raw data about patients’ consent to data-sharing.

In an accompanying editorial, BMJ deputy editor Trish Groves notes that the journal is now adopting some of these recommendations, such as extending its data-sharing statements to include explicit information on patient consent.