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Retrospective vs. prospective registration of clinical trials – what is the norm?

As a prerequisite for publication of research, the International Committee of Medical Journal Editors (ICMJE) requires registration of clinical trials and recommends this to editors of medical journals. Similarly, provision of a registration number is specifically stipulated in the CONSORT and GPP3 publication guidelines. In addition to the ethical obligation for transparency in research, the registration of clinical trials serves many other purposes; it reduces publication and outcome reporting bias, prevents duplication of research, makes the public aware of trials for which they may be eligible and provides context for ethics review committees considering the approval of new studies. To fulfil these purposes, ICMJE encourages prospective registration of clinical trials, ideally before the first patient is enrolled, but how often does this occur in practice?

A recent study in Trials compared the proportion of clinical trials published across 21 journals in the Biomed Central (BMC) series in 2013 that were registered prospectively and retrospectively. In addition, for those registered retrospectively, the study determined whether registration took place before or after submission to the journal in which they were published. Of the 108 studies that met the study’s inclusion criteria, almost one-third (33/108 [31%]) were prospectively registered, 72 (67%) were retrospectively registered and 3 (3%) did not include a registration number. Of the 72 studies registered retrospectively, the vast majority (66/72 [92%]) were registered prior to submission to the journal.

The authors suggested that studies may not have been registered prospectively due to a lack of awareness or understanding of this requirement. It is also possible that some researchers deliberately avoid trial registration in order to selectively report outcomes or avoid publishing negative results.

Many journals, including those in the BMC series, will consider studies that have been retrospectively registered. This can prevent the non-publication of potentially valuable research. However, it does not provide an incentive for researchers to register prospectively. The authors proposed that although journal editors do have a role in promoting and enforcing prospective registration, due to their involvement earlier in the research process, research institutions, grant-giving bodies and ethics approval committees may be better placed to do this. If retrospective registration is to be considered acceptable for trial publication, transparent reporting of this is essential.

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Summary by Alice Wareham, PhD from Aspire Scientific.

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