Background: In generalized epidemics, national HIV prevalence estimates are derived indirectly from surveillance of pregnant women attending selected antenatal care (ANC) clinics. The main advantages of using ANC data include low cost of data collection and accessibility of populations. However, ANC data may not represent HIV prevalence in the general population.
Objectives: The purpose of this study is to compare HIV prevalence estimates obtained from the 2006 ANC surveillance survey with estimates obtained from the 2005-06 population-based Zimbabwe Demographic and Health Survey (ZDHS), and to assess the use of three residential classifications— rural, urban, and other—in deriving HIV estimates.
Methods: Geographic Information Systems were used to match ANC surveillance sites with ZDHS clusters. HIV prevalence estimates from the ANC surveillance sites were compared with estimates from the corresponding ZDHS clusters for all men and women and for women residing within 30km of the ANC sites. Comparisons were also made stratified by current pregnancy status, experience of recent child birth, and receiving ANC for the last birth.
Results: Women in the 2006 ANC survey were more likely to live in urban areas, had fewer children, and were more educated, more likely to be unemployed, and younger than women in the ZDHS sample. The ANC HIV prevalence estimate (17.9%, 95% CI 17.0%–18.8%) was similar to the ZDHS estimates for all men and women age 15-49 years (18.1%, 16.9%–18.8%), for pregnant women (17.5%, 13.9%–21.9%), and for ANC attendees living within 30km of the ANC surveillance sites (19.9%, 17.1%–22.8%). However, the ANC surveillance estimate (17.9%) was significantly lower than the ZDHS estimates for all women (21.1%, 19.7%–22.6%) and for women living within 30km catchment areas of ANC surveillance sites (20.9%, 19.4%–22.3%). HIV prevalence in the ANC sites classified as urban and rural was significantly lower than in sites classified as “other”.
Conclusions: ANC surveillance provides reliable estimates of HIV prevalence among pregnant women attending ANC clinics and is a useful source of data for monitoring the HIV epidemic in Zimbabwe. Data from periodic population-based surveys complement ANC surveillance data by providing nationally representative estimates of HIV prevalence, as well as linked information on the characteristics and behaviors of people. A much higher HIV prevalence among the ANC sites classified as “other” suggests that Zimbabwe should continue to generate HIV estimates using the three classifications: rural, urban, and other.
Key Words: HIV, prevalence, antenatal, surveillance, survey, DHS, Zimbabwe