[1] Kent & Canterbury Hosp, Haemophilia Ctr, Canterbury, Kent, England
[2] Churchill Hosp, Oxford Haemophilia Ctr, Oxford OX3 7LJ, England
[3] Churchill Hosp, Thrombosis Unit, Oxford OX3 7LJ, England
[4] Trafford Gen Hosp, Dept Haematol, Manchester, Lancs, England
[5] UCL Hosp, Dept Haematol, London, England
[6] UCL Hosp, Dept Clin Pharmacol, London, England