1. Medical Division South African National Blood Service Roodepoort South Africa
2. Division of Clinical Haematology, Department of Medicine University of Cape Town Cape Town South Africa
3. Division of Clinical Haematology University of the Free State Bloemfontein South Africa
4. Department of Laboratory Medicine University of California, San Franciscco San Francisco California USA
5. Department of Epidemiology/Biostatistics University of California, San Franciscco San Francisco California USA
6. Epidemiology and Bioinformatics Core Vitalant Research Institute San Francisco California USA
7. Division of Clinical Pharmacology, Department of Medicine University of Cape Town Cape Town South Africa