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Sample size determination for stepped wedge cluster randomized trials in pragmatic settings.

Jijia Wang1, Jing Cao2, Song Zhang3

  • 1Department of Applied Clinical Research, UT Southwestern Medical Center, Dallas, TX, USA.

Statistical Methods in Medical Research
|June 18, 2021
PubMed
Summary

This study provides a flexible sample size calculation for stepped-wedge cluster randomized trials, accommodating common design challenges in health services research. The method aids researchers in planning pragmatic trials with complex features.

Keywords:
Clinical trialsGEEpragmaticsample sizestepped wedge

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Area of Science:

  • Health Services Research
  • Biostatistics
  • Clinical Trial Design

Background:

  • Stepped-wedge cluster randomized designs are increasingly used in pragmatic trials.
  • Existing sample size methods may not fully address the complexities of these designs.

Purpose of the Study:

  • To develop closed-form sample size calculation methods for stepped-wedge trials.
  • To accommodate common design issues in pragmatic trials, including correlation structures, irregular crossovers, and missing data.

Main Methods:

  • Generalized Estimating Equations (GEE) approach.
  • Development of closed-form sample size formulas.
  • Adjustment for underestimated variance in trials with limited clusters.
  • Extensive simulation studies to evaluate the method's performance.

Main Results:

  • The proposed method provides accurate sample size estimates for stepped-wedge trials.
  • Flexibility in accommodating various design complexities.
  • The adjustment approach effectively addresses variance underestimation.

Conclusions:

  • The presented sample size calculation is a valuable tool for researchers designing pragmatic stepped-wedge cluster randomized trials.
  • The method enhances the planning and efficiency of health services research.
  • Researchers can analytically assess design impacts on sample size requirements.