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Reporting of sample size calculation in randomised controlled trials: review
Pierre Charles1, Bruno Giraudeau, Agnes Dechartres
1INSERM, U738, Paris, France.
BMJ (Clinical Research Ed.)
|May 14, 2009
Summary
Sample size calculations in randomized controlled trials are often poorly reported and inaccurate. This review highlights significant discrepancies in reported assumptions and calculations, questioning trial validity.
Area of Science:
- Clinical Trials
- Biostatistics
- Medical Research Methodology
Background:
- Accurate sample size calculation is crucial for the statistical power and validity of randomized controlled trials (RCTs).
- Inadequate reporting or erroneous calculations can lead to underpowered or overpowered studies, affecting results interpretation.
Purpose of the Study:
- To evaluate the quality of sample size calculation reporting in RCTs.
- To assess the accuracy of reported sample size calculations.
- To determine the relevance and accuracy of assumptions used in sample size calculations.
Main Methods:
- Systematic review of primary reports of two-arm parallel-group superiority RCTs published in high-impact general medical journals (2005-2006).
- Assessment of completeness and accuracy of sample size calculation reporting and assumptions.
- Replication of sample size calculations using reported and estimated parameters.
Main Results:
- 5% of RCTs did not report sample size calculations; 43% omitted required parameters.
- 30% of recalculated sample sizes differed by over 10% from reported values.
- Assumptions for control groups differed significantly from observed data in 31% (>30%) and 17% (>50%) of trials.
Conclusions:
- Reporting of sample size calculations in RCTs remains inadequate.
- Calculations are frequently erroneous, and assumptions are often inaccurate.
- These deficiencies raise concerns about the reliability of sample size determination in RCTs.
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