How well do antenatal clinic (ANC) attendees represent the general population? A comparison of HIV prevalence from ANC sentinel surveillance sites with a population-based survey of women aged 15-49 in Cambodia.

BACKGROUND The purpose of this study was to evaluate whether HIV-1 prevalence among antenatal clinic (ANC) attendees in Cambodia provided a reasonable estimate of HIV-1 prevalence among all women 15-49 years. METHODS Antenatal clinic attendees in five HIV sentinel surveillance sites (five provinces) were selected by consecutive sampling (n = 1695). The population survey of females by household was carried out in the same five areas. Household females aged 15-49 years were selected using a three-stage cluster sampling design (n = 3066). Serum-based HIV ELISA testing was done for both ANC attendees and household females. The HIV prevalence for ANC attendees and household females were compared by age group and urban versus rural location. RESULTS The overall prevalence of HIV-1 infection among ANC attendees (1.62%, 95% CI : 1.26-1.98) was similar to the overall prevalence obtained from the general population of household females (1.24%, 95% CI : 0.92-1.55) in the same catchment areas in Cambodia. In the rural areas, the overall HIV prevalence among ANC attendees (2.18%, 95% CI : 1.59-2.77) was significantly higher than among the household females (0.86%, 95% CI : 0.49-1.23) after adjustment for age distribution and education level. In the 15-24 age group in rural areas, the HIV prevalence of ANC women was 2.71% (95% CI : 0.96-4.46) compared with 0.77% (95% CI : 0.02-1.53) in household females. CONCLUSIONS Although ANC data can be used to estimate trends over time, it should be realized that ANC data may overestimate the actual prevalence in the younger age group in rural areas in Cambodia.