1. Department of Clinical Biochemistry, Addenbrooke's Hospital, Cambridge CB2 2QR
2. Poisons Unit, New Cross Hospital, London SE14 5ER
3. Department of Clinical Biochemistry, Queen Elizabeth II Hospital, Welwyn Garden City AL7 4HQ
4. Department of Clinical Biochemistry, St Albans City Hospital, St Albans, Herts AL3 5PN
5. Microbial Technology Laboratory, PHLS Centre for Applied Microbiology and Research, Porton Down, Salisbury, Wilts SP4 0JG