Monitoring the AIDS epidemic using HIV prevalence data among young women attending antenatal clinics: prospects and problems.
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Author(s): Basia Z, Boerma T, White R
Objective: to assess the potential of antenatal surveillance data on HIV prevalence in young women as an indicator of trends in HIV incidence. Design: Review of empirical data and problems encountered with surveillance systems, followed by modelling using cohort-component projections and micro-simulation. Methods: Projection models are used to illustrate dynamic relationship between changes in HIV incidence and prevalence in young pregnant women. Incidence changes due to change in risk among sexually active and change in pattern of sexual debut are explored separately, and the prevalence trends in pregnant women under age 25 and those expecting first two births are described. Micro-simulation models are used to explore effect on steady-state prevalence of co-factors which affect both fertility and HIV incidence. Results: HIV prevalence levels in young pregnant women categorized by age and by parity have different relationships to incidence levels. Age categorized prevalence data provide a reasonable indication of incidence under stable conditions, but may be very misleading if age pattern of sexual debut changes. Prevalence levels categorized by parity are a reliable guide to incidence in the sexually active, but not necessarily to incidence in the community as a whole. Conclusions: Ante-natal surveillance systems should categorize prevalence data by both age and parity to aid in the interpretation of underlying incidence levels.
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