Background: Interventional studies may have high risk of bias, which can mislead medical practice and waste research funding. Reducing or predicting the risk of bias during study design or conduct would help to address this issue.
Objectives: To describe interventions during study design and conduct to reduce the risk of bias in interventional studies.
Methods: This was a scoping review of three electronic bibliographic databases (MEDLINE, Embase, Cochrane Library) and eight grey literature sources (ClinicalTrials.gov, ANZCTR, WHO ICTRP, MedNar, National Guideline Clearinghouse, WHO Guidelines summaries, Analysis & Policy Observatory, Open Grey). Records were included if they described the implementation or effectiveness of an intervention during study design or conduct which aimed to reduce the risk of bias in interventional studies.
Results: We screened 17,334 records from the electronic bibliographic databases and 15,591 records from the grey literature databases. We identified four studies which were eligible for inclusion. These assessed (1) report writing aids, (2) material incentives for study participants, (3) third-party interventions (independent clinical events committee), and (4) education and training for researchers. At the study design stage, a more rigorous participant screening process and systematic participant tracking programme can be designed to ensure a lower rate of lost follow-ups. Financial incentives can be designed for young participants, which will help to increase their response rate and participation. During the conduct phase of the study, an independent clinical committee can avoid the inherent bias of the investigator in judging event outcomes, reduce the risk of bias, and correct the results. Report writing aids could address the current situation of poor adherence to clinical reporting guidelines and significantly reduce the risk of selective reporting.
Conclusions: We identified a few interventions that have reduced risk of bias, which do not encompass all the risks of bias faced by interventional studies. These interventions require adequate research funding and staff support and cannot be applied to all interventional studies. We also identified various pathways to reducing the risk of bias by intervening during study design which have yet to be tested in practice. Patient, public, and/or healthcare consumer involvement: None.