Figure 3. Changes in the probability of testing recent by BED with time since HIV infection.
For PNP = 0 there are no “non-progressors” – i.e. it is assumed that every person, at some point, has a BED OD>C, the pre-set OD cut-off. For PNP>0 some people never have an OD>C. In both cases, however, it is allowed that some cases may revert, temporarily or permanently – i.e. that the OD declines from >0.8 to <0.8. Note that this implies that the level of ε may vary with the time since seroconversion and, in particular, may not even (as illustrated for simplicity) increase monotonically with time.