[1] Stellenbosch Univ, Fac Med & Hlth Sci, Dept Global Hlth, Div Epidemiol & Biostat, POB 241,Francie Van Zyl Dr, ZA-8000 Cape Town, South Africa
[2] McMaster Univ, Dept Hlth Res Methods Evidence & Impact, Hamilton, ON, Canada
[3] Univ Johannesburg, Fac Hlth Sci, Johannesburg, South Africa
[4] St Josephs Healthcare Hamilton, Father Sean OSullivan Res Ctr, Biostat Unit, Biostat, 3Rd Floor Martha Wing, 50 Charlton Ave East, Hamilton, ON L8N 4A6, Canada
[5] Columbia Univ, Vagelos Coll Phys & Surg, Gertude H Sergievsky Ctr, Irving Med Ctr, New York, NY USA
[6] Khayelitsha Dist Hosp, Western Cape Prov Dept Hlth, Cape Town, South Africa
[7] Stellenbosch Univ, Fac Med & Hlth Sci, Family Ctr Res Ubuntu, Dept Paediat & Child Hlth, Tygerberg, South Africa