Dynamic balancing randomization in controlled clinical trials
Article first published online: 30 NOV 2005
Copyright © 2005 John Wiley & Sons, Ltd.
Statistics in Medicine
Special Issue: Papers from the 25th Annual Conference of the International Society for Clinical Biostatistics
Volume 24, Issue 24, pages 3729–3741, 30 December 2005
How to Cite
Heritier, S., Gebski, V. and Pillai, A. (2005), Dynamic balancing randomization in controlled clinical trials. Statist. Med., 24: 3729–3741. doi: 10.1002/sim.2421
- Issue published online: 30 NOV 2005
- Article first published online: 30 NOV 2005
- Manuscript Accepted: 6 SEP 2005
- Manuscript Received: 17 AUG 2005
- biased coin;
- dynamic balancing
In the design of randomized clinical trials, balancing of treatment allocation across important prognostic factors (strata) improves the efficiency of the final comparisons. Whilst randomization methods exist which attempt to balance treatments across the strata (permuted blocks, minimization, biased coin), these approaches assign equal importance for all the strata. Dynamic balancing randomization (DBR) is a tree-based method proposed by Signorini et al. allowing different levels of imbalance in different strata which ensures a balance for each level of prognostic risk factors (conditional balance) whilst at the same time preserving randomness. We present a simple modification to the original approach to maintain a marginal balance over important strata and examine the properties of this modification. Two important measures of performance are used to provide comparisons between the approaches: a loss function, which can be interpreted as the squared norm of the imbalance vector, and a forcing index which conveys the degree of randomness. A comparison of DBR with minimization and a biased coin design is carried out by simulation on two simulated trials. Copyright © 2005 John Wiley & Sons, Ltd.