1. From the Division of Transfusion Medicine, Department of Haematology, University of Cambridge, United Kingdom; National Blood Service, East Anglia Blood Centre, Cambridge, United Kingdom; Public Health Laboratory Service and National Blood Service, London, United Kingdom; Departments of Medicine and Biochemistry, Komfo Anokye Teaching Hospital, Kumasi, Ghana; Chiron Corporation, Emeryville, CA; and Gen-Probe, San Diego, CA.