1. Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
2. Department of Respiratory Medicine, Aintree University Hospital, Liverpool, L9 7AL, UK
3. Department of Information and Computer Technology, Nottingham University Hospitals NHS Trust, Nottingham, NG5 1PB, UK
4. Department of Respiratory Medicine, University of Nottingham, Nottingham, NG5 1PB, UK