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Related Experiment Videos

Sample size calculations in surgery: are they done correctly?

Melinda A Maggard1, Jessica B O'Connell, Jerome H Liu

  • 1UCLA School of Medicine and the West Los Angeles Veterans Affairs Medical Center, Los Angeles, CA 90095, USA.

Surgery
|August 30, 2003
PubMed
Summary

Many surgical randomized controlled trials (RCTs) lack reported sample size calculations, potentially leading to underpowered studies. Over half of underpowered studies required more than a tenfold increase in sample size.

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Area of Science:

  • Surgical research methodology
  • Evidence-based medicine
  • Clinical trial design

Background:

  • Randomized controlled trials (RCTs) are crucial for clinical research.
  • Prior work indicates poor sample size reporting in surgical literature.
  • Inadequate sample size calculations can lead to underpowered studies, increasing Type I and Type II errors.

Purpose of the Study:

  • To assess the reporting of sample size calculations in surgical RCTs.
  • To determine the power of published surgical RCTs to detect treatment effect differences.
  • To identify the extent of underpowering in surgical studies.

Main Methods:

  • A systematic literature search identified RCTs published in leading surgical journals (1999-2002).
  • Two independent reviewers assessed sample size calculation reporting.

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  • Statistical power analysis was conducted to evaluate the ability to detect 50% and 20% effect differences.

    • Main Results:

    • Only 38% of 127 reviewed RCTs reported sample size calculations.
    • 50% of studies were adequately powered for a large (50%) effect difference; only 19% for a small (20%) difference.
    • More than half of underpowered studies needed a >10-fold increase in sample size.

    Conclusions:

    • Over 60% of surgical RCTs lacked reporting of sample size calculations.
    • Approximately 50% of studies were underpowered to detect large treatment effect differences.
    • Underpowered surgical RCTs often require substantial sample size increases.