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BMC Medical Research Methodology
Published in: BMC Medical Research Methodology 1/2008

Open Access 01-12-2008 | Software

Balance algorithm for cluster randomized trials

Authors: Ben R Carter, Kerenza Hood

Published in: BMC Medical Research Methodology | Issue 1/2008

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Abstract

Background

Within cluster randomized trials no algorithms exist to generate a full enumeration of a block randomization, balancing for covariates across treatment arms. Furthermore, often for practical reasons multiple blocks are required to fully randomize a study, which may not have been well balanced within blocks.

Results

We present a convenient and easy to use randomization tool to undertake allocation concealed block randomization. Our algorithm highlights allocations that minimize imbalance between treatment groups across multiple baseline covariates.
We demonstrate the algorithm using a cluster randomized trial in primary care (the PRE-EMPT Study) and show that the software incorporates a trade off between independent random allocations that were likely to be imbalanced, and predictable deterministic approaches that would minimise imbalance. We extend the methodology of single block randomization to allocate to multiple blocks conditioning on previous allocations.

Conclusion

The algorithm is included as Additional file 1 and we advocate its use for robust randomization within cluster randomized trials.
Appendix
Available only for authorised users
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Metadata
Title
Balance algorithm for cluster randomized trials
Authors
Ben R Carter
Kerenza Hood
Publication date
01-12-2008
Publisher
BioMed Central
Published in
BMC Medical Research Methodology / Issue 1/2008
Electronic ISSN: 1471-2288
DOI
https://doi.org/10.1186/1471-2288-8-65

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