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Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index

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Quantifying the exact allocation ratios in randomized clinical trials with biased coin randomization.

Yunzhi Lin¹, Zheng Su

¹University of Wisconsin, Madison, USA.

Computer Methods and Programs in Biomedicine

|May 22, 2012

Summary

Biased coin randomization in clinical trials can lead to unpredictable treatment allocation ratios, impacting trial enrollment and results. A modified permuted block randomization offers improved balance for treatment assignments and stratification variables.

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Area of Science:

Clinical Trials
Biostatistics
Medical Research Methodology

Background:

Biased coin randomization is common in clinical trials for balancing treatment assignments.
However, the exact allocation ratios can deviate significantly from the intended ratio.
This deviation poses challenges for trial enrollment and result interpretation.

Purpose of the Study:

To develop an algorithm for theoretically determining exact allocation ratios in biased coin randomization.
To propose a modified randomization method for maintaining constant allocation ratios.
To assess the balance achieved for treatment assignments and stratification variables.

Main Methods:

Development of an algorithm to calculate exact allocation ratios based on randomization order.
Proposal of a modified permuted block randomization technique.
Comparative analysis of allocation balance between methods.

Main Results:

The study found that biased coin randomization can result in significant deviations from specified allocation ratios.
The proposed modified permuted block randomization method maintains a constant allocation ratio.
This modification also improves balance for baseline stratification variables.

Conclusions:

Biased coin randomization may not guarantee the intended treatment allocation balance throughout a clinical trial.
A modified permuted block randomization is a viable alternative for achieving consistent balance.
This improved balance enhances both trial enrollment and the interpretability of study findings.