The extent of misclassification increases with time, especially in countries where the epidemic has declined.
In both cases, it was speculated that this may be due to patterns of widowing and remarriage, but our modelling indicates that this surprising pattern of incidence over age may, in fact, be due misclassification increasing with time infected.
Another reason why misclassification could increase with time since infection would be if the individuals with fully developed immune-responses that are misclassified as recent live for longer than others.
If a time-varying covariate is fixed to a baseline value in a TTE analysis, the degree of misclassification may increase with time and result in underestimation of the covariate effect.
If the chance of misclassification by BED increases with time since infection, the overall proportion of individuals misclassified could vary widely between countries, over time, and across age-groups, in a manner determined by the historic course of the epidemic and the age-pattern of incidence.
Also, if the individuals with fully developed immune-responses that are misclassified as recent live for longer than others, then misclassification rates will also vary with time since infection [23], [28].
There is also the possibility of misclassification with respect to the time of onset of dementia.
These distributions results in substantial variation in the level of misclassification by the BED test, if the PFP increases with time since infection (scenario B in Figure 1).
Any potential misclassification of standing time as SED-time, however, would likely have led to attenuation of the associations with SED-time.
The exact nature of the relationship between misclassification and time since infection is not known.
