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Assessing methods to specify the target difference for a randomised controlled trial: DELTA (Difference ELicitation
Jonathan A Cook1, Jennifer Hislop1, Temitope E Adewuyi1
1Health Services Research Unit, University of Aberdeen, Aberdeen, UK.
Summary
Determining the target difference is crucial for randomized controlled trial (RCT) sample size calculations. This study reviews methods and current practices, offering guidance to improve trial design and reporting for better evidence evaluation.
Area of Science:
- Clinical Trials Methodology
- Biostatistics
- Health Services Research
Background:
- Randomized controlled trials (RCTs) are the gold standard for health intervention effectiveness studies.
- Accurate sample size calculation, particularly the target difference, is vital for RCT validity and ethical conduct.
- Methods for specifying the target difference in RCTs are often neglected, leading to unclear evidence.
Purpose of the Study:
- To systematically review methods for specifying the target difference in RCT sample size calculations.
- To evaluate current triallist practices through surveys.
- To develop guidance for specifying target differences and identify future research needs.
Main Methods:
- A systematic literature review of methods for specifying the target difference in RCTs.
- Two surveys of triallists (Society for Clinical Trials members and UK/Ireland-based triallists) to assess current practices.
- Development of structured guidance based on review and survey findings.
Main Results:
- Seven methods for specifying the target difference were identified: anchor, distribution, health economic, opinion-seeking, pilot study, review of evidence base (RoEB), and standardized effect size (SES).
- Survey results indicated varying awareness and use of these methods among triallists, with RoEB and pilot study methods being most recognized.
- Formal methods were used by 91% of surveyed UK triallist groups for their most recent trials.
Conclusions:
- There is a significant need for increased utilization of formal methods to determine the target difference in RCTs.
- Improved reporting of target difference specification is essential for enhancing the quality and interpretation of RCT evidence.
- Raising standards in RCT sample size calculations and reporting will benefit healthcare professionals, patients, researchers, and funders.
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