[1] Univ Manchester, Manchester Royal Infirm, Dept Haematol, Manchester M13 9WL, Lancs, England
[2] Univ Oxford, Clin Trial Serv Unit, Oxford, England
[3] Univ Oxford, Canc Epidemiol Unit, Oxford, England
[4] Churchill Hosp, Haemophilia Ctr, Oxford OX3 7LJ, England
[5] Birmingham Childrens Hosp Natl Hlth Serv Trust, Dept Haematol, Birmingham, W Midlands, England
[6] Royal Free Hosp, Haemophilia Ctr, London NW3 2QG, England
[7] Royal Infirm Edinburgh NHS Trust, Haemophilia Ctr, Edinburgh, Midlothian, Scotland