Fig. 1. Test trade-offs at different levels of the health care system.

a, Schematic showing the different levels of health care available from national to community levels, indicating the equipment and tests which are available at each level. Lab-NAT: laboratory-based nucleic acid tests; EIA, enzyme immunoassay; WB, western blot; CLIA, chemiluminescence immunoassay; ECL, electrochemiluminescence immunoassay. b, Key characteristics of diagnostics tests to reflect trade-offs between accuracy, accessibility and affordability for different levels of the health care system. Panel a adapted from ref. ¹⁴, WHO.