[1] Groote Schuur Hosp, Div Dermatol, ZA-7925 Cape Town, Observatory, South Africa
[2] Groote Schuur Hosp, Dept Stat Sci, ZA-7925 Cape Town, Observatory, South Africa
[3] Groote Schuur Hosp, Sch Publ Hlth & Family Med, ZA-7925 Observatory, South Africa
[4] Univ Cape Town, ZA-7925 Cape Town, Observatory, South Africa