[1] Royal Free Hosp, Haemophilia Ctr, London NW3 2QG, England
[2] Royal Free Hosp, Thrombosis Unit, London NW3 2QG, England
[3] Hop St Justine, Haemophilia Treatment Ctr, Montreal, PQ H3T 1C5, Canada
[4] A Bianchi Bonomi Haemophilia & Thrombosis Ctr, Dept Internal Med, Milan, Italy
[5] First Dept Internal Med, Div Haematol & Blood Coagulat, Vienna, Austria
[6] L Sacco Univ Hosp, Milan, Italy