HIV infection among pregnant women in Bobo-Dioulasso, Burkina Faso: comparison of voluntary and blinded seroprevalence estimates

The objective of our study was to estimate the prevalence of HIV infection among pregnant women in Bobo-Dioulasso (Burkina Faso) according to 2 survey methods. Unlinked anonymous HIV screening was performed among women attend ing 2 antenatal clinics. Voluntary and confidential HIV counselling and tes ting were offered to women attending 2 other antenatal clinics in the same time period, September-October 1996. Voluntary HIV testing was performed in the context of a clinical trial on mother-to-child transmission of HIV (AN RS 049 clinical trial) with an acceptance rate of HIV testing of 93%. The f irst survey recruited 200 women and the second, 424. The mean age (24.6 yea rs vs 24.8 years) and the mean number of pregnancies (3.1 vs 3.3) of women were comparable, in the 2 studies (P=0.69 and P=0.26, respectively). Preval ence of HIV infection in the blinded survey was estimated at 10.0% (95% con fidence interval (CI): 6.4-15.2), while it was 9.4% (95% CI: 6.9-12.7) in t he voluntary HIV screening programme. These 2 estimates were not statistica lly different (P=0.82). In the voluntary screening study, the prevalence of HIV infection was significantly different between age groups 15-24 years a nd 25-49 years (13.9% vs 4.5%, P<0.001). Ln the age group 25-49 years, the prevalence of HIV infection estimated in the blinded study and in the volun tary screening study were significantly different (10.5% vs 4.5%, P=0.04) s uggesting a potential participation bias among pregnant women of older age in the voluntary, confidential HIV screening group. In conclusion, for the purpose of HIV surveillance, the most reliable method for HIV prevalence re mains the unlinked, anonymous testing.