Quantifying the Cost in Power of Ignoring Covariate Imbalances in Clinical Trial Randomization

• Activity Number: 668
• Type: Contributed
• Date/Time: Thursday, August 5, 2010 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Jody Dyan Ciolino*+ and Wenle Zhao and Yuko Y. Palesch and Renee' Martin
• Companies: Medical University of South Carolina and Medical University of South Carolina and Medical University of South Carolina and Medical University of South Carolina
• Keywords: clinical trial ; randomization ; prognostic factor ; covariate

Abstract

Motivated by potentially serious imbalances of baseline covariates in clinical trials, we investigated the cost in statistical power of ignoring the balance of covariates in randomization. Based on data from a clinical trial of acute ischemic stroke treatment, computer simulations were used to create scenarios varying from best possible balance to worst possible imbalance, with multiple balancing levels between the two extremes. The likelihood of each scenario occurring under simple randomization was also evaluated. Power of the main effect test for treatment was examined. Our simulation results show that power loss could be nontrivial if balancing of important covariates were ignored. This situation is more serious for trials with a small sample size and for covariates with large influence on primary outcome.