Centre for Immunobiology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK. Electronic address: james.lindsay8@nhs.net. Sheffield Clinical Trials Research Unit, University of Sheffield, Sheffield, UK. Department of Radiology, Nottingham University Hospitals NHS Trust, Nottingham, UK. Department of Haematology, Nottingham University Hospitals NHS Trust, Nottingham, UK. John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK. Department of Gastroenterology, Western General Hospital, Edinburgh, UK. Department of Biostatistics & Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK. Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK. NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK; Translational Medical Sciences, School of Medicine, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, UK. Department of Gastroenterology, Guy's and Saint Thomas' Hospitals NHS Trust, London, UK. King's College Hospital NHS Foundation Trust, London, UK. Department of Gastroenterology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK. Department of Medicine, University of Cambridge, Cambridge, UK. Department of Haematology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK. NIHR Oxford Biomedical Research Centre, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Oxford, UK. Liverpool University Hospitals NHS Foundation Trust, Liverpool, UK. NIHR Biomedical Research Centre, Translational Gastroenterology Unit, Nuffield Department of Experimental Medicine, University of Oxford, Oxford, UK. Department of Clinical Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK. Division of Clinical Medicine, School of Medicine and Population Health, University of Sheffield, Sheffield, UK; Department of Haematology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK.