The prospective registration of a randomized controlled trial (RCT) can reduce bias by clearly laying out the methods to be used before the research is conducted and data analyzed. Registration can also help limit unintentional duplication of efforts, which can be seen as an ethical charge, as duplication of research may mean duplication of unnecessary potential risks to participants and a failure to properly disseminate the findings of research. In 2004, the International Committee of Medical Journal Editors (ICMJE) recommended that journals only consider publishing results of a trial that was prospectively registered.
A new study by Lindsley and colleagues set out to examine just how many RCTs included in a sample of systematic reviews were properly registered, and if so, whether the registration entry was updated with results of the trial. From a group of 618 systematic reviews published within the Cochrane Musculoskeletal, Oral, Skin and Sensory (MOSS) network between 2014 and 2019, between a total of 100 eligible reviews were randomly selected from each of the network's eight groups (30 from the Eyes and Vision group, which provided the pilot data, and ten from each of the remaining seven).
Among a total of 1,432 included trials published since 2000 when the protocol repository clinicaltrials.gov became available, only 379 (26%) had been registered. Of those 1,177 trials published since 2005, when the ICMJE recommendation first went into effect, the proportion of registered trials increased to 31%, and then to 38% for those published since 2010. Registered trials had double the median number of patients (120) than non-registered trials (60). About one-third (31%) of the trials published since 2005 included at least one major outcome within the registry record. While trial registration did seem to increase over time, only during two years - 2015 and 2018 - did the proportion of registered to nonregistered trials exceed 50%.
Overall, the authors found that while trial registration has become more common since 2005, it still tends to make up the minority of trials included within systematic reviews of this area. In addition, only about 10% of trials examined had updated the registration record with results related to safety or efficacy. Much room for improvement remains in terms of increasing and incentivizing the prospective registration of trials and update of information with publicly available results.
Lindsley K, Fusco N, Teeuw H, et al. (2021). Poor compliance of clinical trial registration among trials included in systematic reviews: A cohort study. J Clin Epidemiol 132:79-87.
Manuscript available here.