1. Department of Transfusion Medicine, National Health Service Blood & Transplant Brentwood, Essex, UK
2. Department of Anaesthesia, Royal National Orthopaedic Hospital Stanmore, Middlesex, UK
3. Department of Orthopaedic Surgery, Norfolk & Norwich University Hospital Norwich, Norfolk, UK
4. Department of Anaesthesia, South Manchester University Hospitals NHS Foundation Trust Wythenshaw, Manchester, UK
5. National Comparative Audit, National Health Service Blood & Transplant Oxford, UK