Objective Preregistration of clinical research has been widely implemented and advocated for many reasons: to detect and mitigate publication bias, selective reporting, and undisclosed changes in determination of primary and secondary outcomes. Prospective registration allows for public scrutiny of trials to identify research gaps and to support the coordination of efforts by preventing unnecessary duplication. Retrospective registration undermines many of these reasons but is commonly found. This study provided a comprehensive analysis of retrospective registration and the reporting thereof in publications, as well as associated factors, based on a validated data set of trial registrations and results publications from Germany from 2009 to 2017.

Design The study used a validated and previously published data set1,2 of trials registered on ClinicalTrials.gov or DRKS (German Clinical Trials Register), led by German University Medical Centers, completed between 2009 and 2017, and with at least 1 peer-reviewed results publication. From all results publications of retrospectively registered trials, all registration statements, including mentions and justifications of retrospective registration, were extracted. Associations between key trial variables and different registration and reporting practices were analyzed.

Results Based on an analysis of 1030 retrospectively registered clinical trials, 2.0% (21) explicitly reported the retrospective registration in the abstract and 3.3% (34) in the full text. In 2.3% (24) of publications, a justification or explanation was provided in the full text. Analyses are ongoing; full results will be presented at the conference, including a qualitative analysis of the reasons given for retrospective registration, as well as trends over time and exploratory analyses of the associations between retrospective registration and other reporting practices, such as registration number reporting and cross-registration practices between different registries.

Conclusions Disclosure of retrospective registration would be a positive signal for rigor, as the registrants would feel it critical to transparently report this limitation. However, only a small number of retrospectively registered studies reported the retrospective nature of the registration. Lack of disclosure might lead readers to wrongly interpret the registration as a quality criterion that, in the case of a retrospective registration, rather describes a concern. This study provided a detailed analysis of this issue.

References

1. Riedel N, Wieschowski S, Bruckner T, et al. Results dissemination from completed clinical trials conducted at German university medical centers remained delayed and incomplete: the 2014-2017 cohort. J Clin Epidemiol. 2022;144:1-7. doi:10.1016/j.jclinepi.2021.12.012
2. Wieschowski S, Riedel N, Wollmann K, et al. Result dissemination from clinical trials conducted at German university medical centers was delayed and incomplete. J Clin Epidemiol. 2019;115:37-45. doi:10.1016/j. jclinepi.2019.06.002

Conflict of Interest Disclosures Daniel Strech is a member of the Sanofi Advisory Bioethics Committee and receives an honorarium for his contribution to meetings. No other disclosures were reported.

Funding/Support The project was funded from QUEST departmental resources.

Additional Information Daniel Strech is a co–corresponding author.