Defining the Features of Registry Based Randomised Controlled Trials (rRCT): A Systematic Review

Abstract Background: Registry Based Randomised Controlled Trials have been described as pragmatic studies utilising patient data embedded in large scale registries, to facilitate key clinical trial procedures such as case report completion, randomisation and follow up data. While the practice of utilising registries to support the conduct of randomised trials is increasing, the reporting of how a registry is used within a trial can vary, causing difficulty in identifying registry based randomised trials and interpreting their exact definition. Methods: The databases PubMed, Embase, Cinahl Plus, Scopus and the Cochrane Central Register of Controlled Trials will be searched using a combination of subject headings, MeSH and free text terms. Search terms will be adapted accordingly for each database, with English language articles included and no other filters applied. Also, grey literature and reference lists will be searched, contacting trial authors for clarification when necessary. Two independent reviewers will complete study screening, selection and quality assessment. A preliminary synthesis will be conducted tabulating the relevant evidence into separate data extraction tables. A narrative synthesis approach will be adopted based on the Guidance on the Conduct of Narrative Synthesis in Systematic Reviews.Results: The present study will synthesise existing registry based randomised trial literature and define their key features.Conclusions: It is essential that trialists and researchers can review published trials and endeavour to duplicate trial designs. There is a lack of consensus in terms of the reporting of registry based randomised trials, making replication of this emerging trial design difficult. This review will clearly summarise and define the key features of these randomised trials, to allow researchers understand and reproduce the novel registry based randomised controlled trial methodology. Systematic Review Registration: PROPSERO CRD42020192419