1. NHS Blood and Transplant, John Radcliffe Hospital, Oxford, UK
2. Translational Gastroenterology Unit, John Radcliffe Hospital, Oxford, UK
3. Medical Research Council Clinical Trials Unit, London, UK
4. NHS Blood and Transplant Clinical Studies Unit, Cambridge, UK
5. Division of Epidemiology and Public Health, and Nottingham Digestive Disease Centre, University of Nottingham, Nottingham, UK
6. Royal Victoria Infirmary, Newcastle, UK
7. Western General Hospital, Edinburgh, UK