PhD ThesisRe-randomisation trials allow patients to be re-enrolled and re-randomised for
each new treatment episode they experience. For example, in a trial evaluating
treatments for acute sickle cell pain crises, patients could be re-randomised each
time they have a new pain crisis. However, uptake of this design has been slow,
likely because of uncertainty around its validity. The purpose of this thesis is to
evaluate the methodological properties of the re-randomisation design.
Chapter 2 defines a set of treatment estimands that can be used for rerandomisation
trials, and chapters 3 and 4 evaluate the use of independence
estimators and mixed-effects models for these estimands. I find that independence
estimators are generally unbiased, though can be biased for certain estimands
in specific situations. Mixed-effects models are generally biased, except under
very strong assumptions. In Chapter 5 I compare re-randomisation with cluster,
crossover, and parallel group designs. I find that re-randomisation compares
favourably with the other designs, though depending on the specific research
question (i.e. estimand of interest), other designs may be more appropriate in
certain settings. In chapter 6 I evaluate a set of trials of granulocyte colonystimulating
factors for patients with febrile neutropenia which include both
parallel group and re-randomisation designs. I found that using re-randomisation
led to an increase in recruitment and provided similar results to parallel group
trials. In conclusion, the re-randomisation design is a valid design option, and
should be used more often
