Defining key design elements of registry-based randomised controlled trials: a scoping review

BACKGROUND: Traditional randomised controlled trials remain the gold standard for improving clinical care but they do have their limitations, including their associated high costs, high failure rate and limited external validity. An alternative methodology is the newly defined, prospective, registry-based randomised controlled trial (RRCT), where treatment and outcome data is collected in an existing registry. This scoping review explores the current literature regarding RRCTs to help identify the key design elements of RRCTs and the characteristics of clinical registries on which they are reliant on. METHODS: A scoping review methodology conducted in accordance with the Joanna Briggs Institute guidelines was performed. Four databases were searched for articles published from inception to June 2018: Medline; Embase; the Cumulative Index to Nursing and Allied Health Literature and; Scopus. The search strategy included MeSH and text words related to RRCT. RESULTS: We identified 2369 articles of which 75 were selected for full-text screening. Of these, only 17 articles satisfied our inclusion criteria. All studies were published between 1996 and 2017 and all were investigator-initiated. Study designs were mainly multi-site comparative/effectiveness studies incorporating the use of disease registries (n = 8), procedure registries (n = 8) and a health services registry (n = 1). The low cost, reduced administrative burden and enhanced external validity of RRCTs make them an attractive research methodology which can be used to address questions of public health importance. We identified that that there are variable definitions of what constituted a RRCT and that issues related to ethical conduct and data integrity, completeness, timeliness, validation and endpoint adjudication need to be carefully addressed. CONCLUSION: RRCTs potentially have an important role to play in informing best clinical practice and health policy. There are a number of issues that need to be addressed to optimise the utility of this approach, including establishing universally accepted criteria for the definition of a RRCT.