1. Manchester University Department of Haematology, Manchester Royal Infirmary, Manchester, United Kingdom;
2. The United Kingdom National Haemophilia Database, Manchester, United Kingdom;
3. Department of Haematology, Glasgow Hospital for Sick Children, Yorkhill, Glasgow, United Kingdom;
4. Department of Haematology, Great Ormond Street Hospital, London, United Kingdom;
5. Department of Haematology, The Royal Hallamshire Hospital, Sheffield, United Kingdom;
6. The Department of Haematology, St Thomas' Hospital, London, United Kingdom;
7. The Department of Haematology, Birmingham Children's Hospital, Birmingham, United Kingdom; and
8. The University Department of Haematology, University Hospital of Wales Hospital, Cardiff, United Kingdom