  Selective recruitment designs preferentially recruit individuals that are
estimated to be statistically informative onto a clinical trial. Individuals
that are expected to contribute less information have a lower probability of
recruitment. Furthermore, in an information-adaptive design recruits are
allocated to treatment arms in a manner that maximises information gain. The
informativeness of an individual depends on their covariate (or biomarker)
values and how information is defined is a critical element of
information-adaptive designs. In this paper we define and evaluate four
different methods for quantifying statistical information. Using both
experimental data and numerical simulations we show that selective recruitment
designs can offer a substantial increase in statistical power compared to
randomised designs. In trials without selective recruitment we find that
allocating individuals to treatment arms according to information-adaptive
protocols also leads to an increase in statistical power. Consequently,
selective recruitment designs can potentially achieve successful trials using
fewer recruits thereby offering economic and ethical advantages.
