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Navigating blinding challenges in complex intervention trials: insights from a UK researcher survey
Abdullah Yonis1, Sarah Gerard Dean2, Fiona C Warren2
1Department of Health and Community Sciences, Medical School, University of Exeter, Exeter, UK. ay302@exeter.ac.uk.
Trials
|November 13, 2025
Summary
Researchers find blinding in complex intervention trials challenging due to intervention complexity and resource limits. Improved stakeholder engagement and clearer guidance are needed to enhance blinding strategies and reduce bias in randomized controlled trials.
Area of Science:
- Methodology in clinical trials
- Biomedical research methodology
Background:
- Blinding is a methodological challenge in complex intervention randomized controlled trials (RCTs).
- Participants and providers often cannot be blinded, potentially lowering evidence ratings.
- Outcome assessor blinding is underutilized, with unclear reasons for limited adoption.
Purpose of the Study:
- To explore UK researchers' attitudes and practices regarding blinding in complex intervention RCTs.
- To understand challenges and facilitators of outcome assessment blinding.
Main Methods:
- An online survey was conducted.
- Targeted researchers affiliated with UK Clinical Research Collaboration (UKCRC) Clinical Trials Units (CTUs), National Institute for Health and Care Research (NIHR), Trials Methodology Research Partnership (TMRP), and NHS-NIHR research units.
Main Results:
- 91% agreed complex interventions pose blinding challenges; 45% cited concerns about internal validity.
- 66% found outcome assessment blinding feasible, but 52% identified limited resources as an obstacle.
- Respondents noted practical constraints, additional costs, and a lack of specific blinding recommendations.
Conclusions:
- Blinding in complex intervention RCTs faces challenges from intervention complexity and resource constraints.
- Outcome assessment blinding feasibility varies, necessitating better methodological guidance.
- Stakeholder involvement is crucial for addressing blinding challenges and improving strategies.
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