Abstract
ObjectivesThe objective of the study was to examine whether clinical trials that have been included in systematic reviews have been registered in clinical trial registers and, when they have, whether results of the trials were included in the clinical trial register. Study Design and SettingThis study used a sample of 100 systematic reviews published by the Cochrane Musculoskeletal, Oral, Skin and Sensory Network between 2014 and 2019. ResultsWe identified 2,000 trials (369,778 participants) from a sample of 100 systematic reviews. The median year of trial publication was 2007. Of 1,177 trials published in 2005 or later, a clinical trial registration record was identified for 368 (31%). Of these registered trials, 135 (37%) were registered prospectively and results were posted for 114 (31%); most registered trials evaluated pharmaceutical interventions (62%). Of trials published in the last 10 years, the proportion of registered trials increased to 38% (261 of 682). ConclusionAlthough some improvement in clinical trial registration has been observed in recent years, the proportion of registered clinical trials included in recently published systematic reviews remains less than desirable. Prospective clinical trial registration provides an essential role in assessing the risk of bias and judging the quality of evidence in systematic reviews of intervention safety and effectiveness.
Highlights
Systematic reviews of randomized clinical trials produce the highest level of evidence for informing the effectiveness of health care interventions [1]
The objectives of the study were to examine whether clinical trials that have been included in systematic reviews have been registered in clinical trial registers (e.g., ClinicalTrials.gov) and, when they have, whether results of the trials were included in the clinical trial register
We examined potential factors that may be associated with clinical trial registration based on the following criteria: condition, type of intervention, number of participants (!100; 100 or more), trial date, and the review authors’ conclusions
Summary
Systematic reviews of randomized clinical trials produce the highest level of evidence for informing the effectiveness of health care interventions [1]. The methods of trials should be outlined before conducting the trial, and deviations should be documented. Clinical trial registers allow trial investigators to prospectively register their intention to conduct a trial and the main methods and outcomes of the trial before enrolling the first trial participant. If trials are not made known to the public and their results are not disseminated, the implicit agreement between the study participant and researcher is broken. This is a form of research waste which may result in duplicate studies being conducted to examine research questions which may already have been answered by previously conducted studies
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