Abstract
Clinical trial registries are important for gaining an overview of ongoing research efforts and for deterring and identifying publication bias and selective outcome reporting. The reliability of the information in trial registries is uncertain. To assess the reliability of information across registries for trials with multiple registrations. For this systematic review, 360 protocols of randomized clinical trials (RCTs) approved by research ethics committees in Switzerland, the UK, Canada, and Germany in 2012 were evaluated. Clinical trial registries were searched from March to September 2019 for corresponding registrations of these RCTs. For RCTS that were recorded in more than 1 clinical trial registry, key trial characteristics that should be identical among all trial registries (ie, sponsor, funding source, primary outcome, target sample size, trial status, date of first patient enrollment, results available, and main publication indexed) were extracted in duplicate. Agreement between the different trial registries for these key characteristics was analyzed descriptively. Data analyses were conducted from May 1 to November 30, 2020. Representatives from clinical trial registries were interviewed to discuss the study findings between February 1 and March 31, 2021. The analysis included 197 RCTs registered in more than 1 trial registry (151 in 2 registries and 46 in 3 registries), with 188 trials in ClinicalTrials.gov, 185 in the European Union Drug Regulating Authorities Clinical Trials Database (EudraCT), 20 in ISRCTN, and 47 in other registries. The agreement of key information across all registries was as follows: 178 of 197 RCTs (90%; 95% CI, 85%-94%) for sponsor, 18 of 20 (90%; 95% CI, 68%-99%) for funding source (funding was not reported on ClinicalTrials.gov), 154 of 197 (78%; 95% CI, 72%-84%) for primary outcome, 90 of 197 (46%; 95% CI, 39%-53%) for trial status, 122 of 194 (63%; 95% CI, 56%-70%) for target sample size, and 43 of 57 (75%; 95% CI, 62%-86%) for the date of first patient enrollment when the comparison time was increased to 30 days (date of first patient enrollment was not reported on EudraCT). For results availability in trial registries, agreement was 122 of 197 RCTs (62%; 95% CI, 55%-69%) for summary data reported in the registry and 91 of 197 (46%; 95% CI, 39%-53%) for whether a published article with the main results was indexed. Different legal requirements were stated as the main reason for inconsistencies by representatives of clinical trial registries. In this systematic review, for a substantial proportion of registered RCTs, information about key trial characteristics was inconsistent across trial registries, raising concerns about the reliability of the information provided in these registries. Further harmonization across clinical trial registries may be necessary to increase their usefulness.
Highlights
Randomized clinical trials (RCTs) are at the top of classical textbook evidence-based medicine pyramids.1,2 randomized clinical trial (RCT) reach their full potential only if they are designed, conducted, and reported appropriately
In this systematic review, for a substantial proportion of registered RCTs, information about key trial characteristics was inconsistent across trial registries
We presented our results and invited them to a short interview to discuss the following key points: [1] Do you plan to work toward more harmonization of registry items across registries? [2] Do you know of any developments since 2012 that could have improved the reliability of information available in clinical trial registries? [3] What measures could be undertaken to improve the agreement of clinical trial registries? Could other stakeholders, such as funding agencies, research ethics committees, or academic institutions, have a role here? and [4] Are you aware of other studies that investigated the consistency of RCT information across registries? Interviews were recorded with the oral permission of clinical trial registry representatives
Summary
Randomized clinical trials (RCTs) are at the top of classical textbook evidence-based medicine pyramids. RCTs reach their full potential only if they are designed, conducted, and reported appropriately. In an article in 2003, Dickersin and Rennie highlighted the lack of transparent overview of clinical research and concluded that “a comprehensive register of initiated clinical trials, with each trial assigned a unique identifier, would inform reviewers, physicians, and others (eg, consumers) about which trials had been started and directly address the problem of publication bias.”. Clinical trial registries are well established and are supposed to provide a comprehensive overview of all ongoing RCTs on a specific topic to help deter unnecessary duplication of research and to estimate and deter publication bias.. Clinical trial registries can be used as a tool to assess whether outcomes are reported in the final published article as previously specified or whether the primary outcome was changed and new outcomes were introduced.. Clinical trial registries are well established and are supposed to provide a comprehensive overview of all ongoing RCTs on a specific topic to help deter unnecessary duplication of research and to estimate and deter publication bias. outcomes must be prespecified in clinical trial registries, which should discourage authors from cherry-picking results in RCTs. clinical trial registries can be used as a tool to assess whether outcomes are reported in the final published article as previously specified or whether the primary outcome was changed and new outcomes were introduced. The ongoing COVID-19 pandemic has further underlined the importance of clinical trial registries for providing an overview of ongoing research efforts and, for creating synergies. the reliability of the information found on clinical trial registration websites remains uncertain. Because some trials are registered in more than 1 clinical trial registry (eg, owing to different requirements by the sponsor and funder or by different participating countries), we empirically assessed the reliability of information on RCTs available in multiple clinical trial registries
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