Location of a hierarchy of HIV/AIDS test laboratories in an inbound hub network:case study in South Africa

HIV/AIDS test laboratories in South Africa face growing demand for high quality, timely and efficient testing of blood samples in all regions of the country, however rural. The three main tests for HIV/AIDS, namely CD4, HIV Viral Load, and Infant PCR, are provided in a hierarchy of levels: CD4 is the most frequently needed test, with most laboratory coverage needed. HIV Viral Load is less frequently called for, and Infant PCR is the rarest test to be done, with correspondingly fewest laboratories needed. The National Health Laboratory Service (NHLS) of South Africa operates an inbound hub network for collection of blood samples and transfer to laboratories equipped to carry out the required tests: test results are transmitted electronically, so there is no outbound or return transport. This paper describes the development of modelling carried out over several years of collaboration with NHLS to advise decision-makers on an appropriate and efficient hub network. We present mixed integer programs to find efficient locations for both network hubs and locations for all levels of laboratory testing. Novel features include variable or range constraints on maximum travel times to test locations.