A non-parametric method for the reconstruction of age- and time-dependent incidence from the prevalence data of irreversible diseases with differential mortality

A method is proposed for reconstructing the time and age dependence of inci dence rates from successive age-prevalence cross sections taken from the se ntinel surveys of irreversible diseases when there is an important differen ce in mortality between the infected and susceptible subpopulations. The pr evalence information at different time-age points is used to generate a sur face; the time-age variations along the life line profiles of this surface and the difference in mortality rates are used to reconstruct the time and age dependence of the incidence rate. Past attempts were based on specified parametric forms for the incidence or on the hypothesis of time-invariant forms for the age-prevalence cross sections. The proposed method makes no s uch assumptions and is thus capable of coping with rapidly evolving prevale nce situations. In the simulations carried out, it is found to be resilient to important random noise components added to a prescribed incidence rate input. The method is also tested on a real data set of successive HIV age-p revalence cross sections from Burundi coupled to differential mortality dat a on HIV+ and HIV- individuals. The often-made assumption that the incidenc e rate can be written as the product of a calendar time component and an ag e component is also examined. In this case, a pooling procedure is proposed to estimate the time and the age profiles of the incidence rate using the reconstructed incidence rates at all time-age points. (C) 1999 Academic Pre ss.