Sentinel surveillance for HIV-1 among pregnant women in a developing country: 3 years' experience and comparison with a population serosurvey

Objectives: To establish unlinked, anonymous sentinel surveillance for HIV-1 among pregnant women attending an antenatal clinic, to determine age-specific seroprevalences, to monitor trends and to compare seroprevalence with that detected by a population serosurvey. To establish the sustainability and costs of surveillance. Design: Sentinel surveillance for HIV through serial collection of unlinked, anonymous seroprevalence data from antenatal care, comparison of sentinel data with those from a population serosurvey; financial and general audit of the sentinel surveillance. Setting: A community antenatal clinic in a large urban centre, Mwanza Municipality, Tanzania, eastern Africa, between October 1988 and September 1991. Patients: Pregnant women attending for antenatal care. Main outcome measure: Age-specific HIV-1 seroprevalences, trends over time, difference from age-specific population seroprevalences, sustainability and costs. Results: Overall HIV-1 seroprevalence was 11.5% (95% confidence interval, 10.5-12.4); differences in age-specific prevalences were not significant. There was no clear evidence of change in seroprevalence over the study period in any age group, although there was some indication of a rise in some age groups in 1988-1989. Sentinel surveillance among pregnant women may have significantly underestimated population HIV-1 seroprevalence for women under the age of 35 years. HIV-1 surveillance proved feasible and sustainable. Additional recurrent costs were US$1.7 per specimen for unlinked anonymous testing and US$0.57 per woman for syphilis screening. Conclusions: HIV-1 seroprevalence did not change significantly over 3 years, probably implying a substantial incidence of HIV-1 infection. In this setting seroprevalence in pregnant women may have underestimated population seroprevalence in women aged under 35 years. With modest inputs and good organization unlinked anonymous HIV-1 sentinel surveillance of pregnant women can be introduced and sustained in an African setting. This may usefully be carried out in conjunction with syphilis screening.