Monitoring the AIDS epidemic using HIV prevalence data among young women attending antenatal clinics: Prospects and problems

Objective: To assess the potential of antenatal surveillance data on HIV pr evalence in young women as an indicator of trends in HIV incidence. Design: Review of empirical data and discussion of problems encountered wit h surveillance systems, illustrated using cohort-component projection model s. Methods: Simple descriptive analyses are presented of prevalence and incide nce data, with projection models used to explore aspects of the dynamic rel ationships between changes in HIV incidence and prevalence in young pregnan t women for which empirical data are not yet available; Incidence changes d ue to change in risk among sexually active, and change in pattern of sexual debut are explored separately, and the resulting prevalence trends in preg nant women under age 25 years, and those expecting their first two births a re described. Results: HIV prevalence levels in young pregnant women categorized by age a nd by parity have different relationships to recent incidence levels. Age c ategorized prevalence data provide a reasonable indication of incidence und er stable conditions, but may be very misleading in the age pattern of sexu al debut changes. Prevalence levels categorized by parity are a reliable gu ide to incidence in the sexually active, but not necessarily to incidence i n the population as a whole. Conclusions: Ante-natal surveillance systems should categorize prevalence d ata by both age and parity to aid in the interpretation of underlying incid ence levels. (C) 2000 Lippincott Williams & Wilkins.