Reducing risk of bias in interventional studies during their design and conduct: a scoping review

Interventional studies are intended to provide robust evidence. Yet poorly designed or conducted studies may bias research results and skew resulting evidence. While there have been advances in the assessment of risk of bias, it is unclear how to intervene against risks of bias during study design and conduct.

To identify interventions to reduce or predict risk of bias in interventional studies during their design and conduct.

For this scoping review, we searched three electronic bibliographic databases (MEDLINE, Embase, and Cochrane Library) and nine grey literature sources and Google from in September 2024. This was supplemented by a natural language processing fuzzy matching search of the top 2000 relevant publications in the electronic bibliographic databases. Publications were included if they described the implementation and effectiveness of an intervention during study design or conduct aimed at reducing risk of bias in interventional studies. The characteristics and effect of the interventions were recorded.

We identified, and reviewed the title and abstracts of, a total of 41,793 publications, reports, documents and grey literature, with 24,677 from electronic bibliographic databases and 17,140 from grey literature sources. There were 67 publications from bibliographic databases and 24 items from grey literature that were considered potentially eligible for inclusion, and the full-text of these were reviewed. Only three studies met the inclusion criteria. The first intervention was offering education and training to researchers during study design. This training included the implementation of a more rigorous participant screening process and systematic participant tracking program that reduced loss to follow-up and missing data, particularly for long-term follow-up trials. The second intervention was introducing an independent clinical events committee during study conduct. This was intended to mitigate bias due to conflicts of interest affecting the analysis and interpretation of results. The third intervention was to provide participants with financial incentives in randomized controlled trials, so that participants could more actively accomplish the requirements of the trials.

Despite the major impact of risk of bias on study outcomes, there are few empirical interventions to address this during study design or conduct.