Published registered reports are rare, limited to one journal group, and inadequate for randomized controlled trials in the clinical field.

OBJECTIVE: Registered reports (RR) are a publication format implying a peer-review of the protocol before the start of the study, followed by an in-principle acceptance (IPA) by the journal before the study starts. We aimed to describe randomized controlled trials (RCTs) in the clinical field published as RR. STUDY DESIGN AND

SETTING: This cross-sectional study included RR results for RCTs, identified on PubMed/Medline and on a list compiled by the Center for Open Science. It explored the proportion of reports that received IPA (and/or published a protocol before inclusion of the first patient) and changes in the primary outcome.

RESULTS: A total of 93 RCTs publications identified as RR were included. All but one were published in the same journal group. The date of the IPA was never documented. For most of these reports (79/93, 84.9%), a protocol was published after the date of inclusion of the first patient. A change in the primary outcome was noted in 40/93 (44%) of them. Thirteen of the 40 (33%) mentioned this change.

CONCLUSIONS: RCTs in the clinical field identified as RR were rare, originated from a single journal group, and did not comply with the basic features of this format.