1. The Global Fund to Fight AIDS, Tuberculosis, and Malaria; Geneva Switzerland
2. School of Public Health; University of the Western Cape; Belleville South Africa
3. Biostatistics Unit; South African Medical Research Council; Hatfield South Africa
4. Department of Statistics; University of Pretoria; Hatfield South Africa
5. Health Systems Research Unit; South African Medical Research Council; Tygerberg South Africa
6. School of Public Health and Family Medicine; University of Cape Town; Cape Town South Africa
7. International Maternal and Child Health, Department of Women's and Children's Health; Uppsala University; Uppsala Sweden