Related Experiment Video
Updated: Dec 19, 2025
04:53
A Clinical Trial Assessing the Safety, Efficacy, and Delivery of Olive-Oil-Based Three-Chamber Bags for Parenteral Nutrition
Published on: September 20, 2019
11.0K
Changes to aspects of ongoing randomised controlled trials with fixed designs.
Xanthi Coskinas1, John Simes1, Manjula Schou2,3
1The National Health and Medical Research Council Clinical Trial Centre, University of Sydney, Camperdown, NSW, 2050, Australia.
Trials
|June 5, 2020
Summary
Modifying clinical trial designs requires care. Legitimate changes, made without knowledge of treatment allocation, maintain unbiased results. Illegitimate changes, however, introduce significant bias and inflate error rates in randomised clinical trials.
Area of Science:
- Clinical Trials Methodology
- Biostatistics
- Evidence-Based Medicine
Background:
- Randomised clinical trials (RCTs) may require design modifications despite initial planning.
- Distinguishing between legitimate and illegitimate changes is crucial for trial integrity.
Purpose of the Study:
- To differentiate legitimate from illegitimate changes in ongoing RCTs.
- To provide guidance for clinical trialists and stakeholders on managing trial modifications.
Main Methods:
- Simulated trial datasets were generated under null (H0) and alternative (H1) hypotheses.
- Assessed strategies of design/analysis changes with (illegitimate) versus without (legitimate) knowledge of treatment allocation.
- Evaluated performance using Type 1 error rates and treatment effect bias.
Main Results:
- Illegitimate changes caused 61% relative bias (H1) and 23% Type 1 error rate (H0).
- Legitimate changes yielded unbiased estimates (H1) without inflating Type 1 error (H0).
Conclusions:
- Modifications to RCT design/analysis may be necessary due to unforeseen circumstances.
- Changes made with knowledge of treatment allocation risk introducing bias.
- Legitimate changes must be documented to ensure validity and stakeholder confidence.
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