2 Imperial College London, London, UK c.lees@imperial.ac.uk p.brocklehurst@bham.ac.uk.
3 Department of Development and Regeneration, KU Leuven, Belgium.
4 Birmingham Clinical Trials Unit, Institute of Applied Health Research, University of Birmingham, Birmingham, UK c.lees@imperial.ac.uk p.brocklehurst@bham.ac.uk.