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How to reduce the number of patients needed for randomized trials: a basic introduction
1Integrative Medicine Service, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. vickersa@mskcc.org
Complementary Therapies in Medicine
|August 20, 2002
Summary
Reducing patient numbers in clinical trials for complementary therapies is possible. Using repeat measurements and analysis of co-variance (ANCOVA) can significantly decrease sample sizes, offering economic and ethical benefits.
Area of Science:
- Clinical Trials Methodology
- Biostatistics
- Complementary Medicine Research
Background:
- Complementary therapies are frequently employed for chronic conditions.
- Standard randomized trials assess patients at baseline and follow-up.
- Reducing sample size in clinical trials has economic and ethical advantages.
Purpose of the Study:
- To investigate methods for reducing patient numbers in clinical trials.
- To evaluate the effectiveness of repeat measurements and ANCOVA in sample size reduction.
- To demonstrate these methods using a trial of acupuncture for back pain.
Main Methods:
- Utilizing repeat measurements of symptom severity.
- Applying analysis of co-variance (ANCOVA) to baseline data.
- Comparing sample sizes with and without these statistical techniques.
Main Results:
- Administering pain questionnaires twice at baseline and four times at follow-up reduced patient numbers by approximately 20%.
- Analysis of co-variance (ANCOVA) further decreased patient numbers by approximately 10%.
- Combined methods can reduce overall sample size by approximately one-third.
Conclusions:
- Repeat measurements and ANCOVA are effective strategies for reducing sample size in clinical trials.
- These methods offer significant economic and ethical benefits by reducing patient numbers.
- ANCOVA requires statistical expertise due to its complexity.