1. Non-Communicable Diseases Research Unit, South African Medical Research Council, Cape Town 7505, South Africa
2. Division of Chemical Pathology, Department of Pathology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town 7505, South Africa
3. National Health Laboratory Service (NHLS), Tygerberg Hospital, Cape Town 7505, South Africa
4. School of Public Health, University of the Western Cape, Bellville 7535, South Africa
5. Human and Social Capabilities, Human Sciences Research Council, Cape Town 8000, South Africa
6. Department of Medicine, University of Cape Town, Cape Town 7925, South Africa