1. Department of Medicine, Groote Schuur Hospital and University of Cape Town, Cape Town, South Africa
2. Division of Rheumatology, Chris Hani Baragwanath Academic Hospital, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
3. The South African National Bioinformatics Institute/Medical Research Council of South Africa Bioinformatics Unit, University of the Western Cape, Belville, South Africa
4. Department of Medicine, University of Cambridge, School of Clinical Medicine, Cambridge, UK