Adjusting ante-natal clinic data for improved estimates of HIV prevalence among women in sub-Saharan Africa

Objectives: To find a simple and robust method for adjusting ante-natal cli nic data on HIV prevalence to represent prevalence in the general female po pulation in the same age range, allowing for fertility differences by HIV s tatus. Background: HIV prevalence comparisons for pregnant women and women in the general community show that prevalence in the latter is significantly highe r than in the former. An adjustment procedure is needed that is specific fo r the demographic and epidemiological circumstances of a particular populat ion, making maximum use of data that can easily be collected in ante-natal clinics or are widely available from secondary sources. Methods: Birth interval length data are used to allow for subfertility amon g HIV-positive women. To allow for infertility, relative HIV prevalence rat ios for fertile and infertile women obtained in community surveys in popula tions with similar levels of contraception use are applied to demographic s urvey data that describe the structure of the population not at risk of chi ld-bearing. Results: For populations with low contraception use, the procedure yields e stimates of general female HIV prevalence of 35-65% higher than the observe d ante-natal prevalence, depending on population structure. Results were ve rified using general population prevalence data collected in Kisesa (Tanzan ia) and Masaka (Uganda). For high contraception use populations, adjusted v alues range from 15% higher to 5% lower, but only limited verification has been possible so far. Conclusions: The procedure is suitable for estimating general female HIV pr evalence in low contraception use populations, but the high contraception v ariant needs further testing before it can be applied widely. (C) 2000 Lipp incott Williams & Wilkins.