[1] Univ Witwatersrand, Sch Clin Med, Dept Internal Med, Fac Hlth Sci, Johannesburg, South Africa
[2] Univ Witwatersrand, Sch Publ Hlth, Fac Hlth Sci, Johannesburg, South Africa
[3] Wits Hlth Consortium, Hlth Econ & Epidemiol Res Off, Johannesburg, South Africa
[4] Boston Univ, Ctr Global Hlth & Dev, Boston, MA 02215 USA
[5] Right Care, Johannesburg, South Africa
[6] Boston Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA USA