1. Analytical Unit, Department of Clinical Pharmacology, St Bartholomew's Hospital, London EC1A 7BE
2. Department of Clinical Chemistry, Royal Liverpool University Hospital, Liverpool L7 8XP
3. Institute of Liver Studies, King's College School of Medicine & Dentistry, London SE5 9PJ
4. Department of Clinical Biochemistry, Addenbrooke's Hospital NHS Trust, Cambridge CB2 2QR, UK