When are clinical trials registered? An analysis of prospective versus retrospective registration

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 Conclusions

Despite the requirement for prospective registration of clinical trials in many journals for the past ten years, this study is the first to show that a large number of clinical trials were not prospectively registered.

The lack of prospective registration identified in this study demonstrates that more needs to be done to improve adherence to prospective registration. It also highlights the importance of allowing retrospective trial registration of studies that have not been prospectively registered in order to prevent the non-publication of potentially valuable research for which human participants have given up their time and exposed themselves to risk.

The results also suggest that there is a need for clear linkage of published articles reporting clinical trials to their trial registry records. This, along with the transparent inclusion of the date of registration in the published article and clear indication in the trial registry record when a trial has been registered retrospectively, will increase transparency and ensure that readers are aware of whether a clinical trial has been prospectively or retrospectively registered.