HIV antibody testing on serum samples was carried out using Enzygnost* Anti-HIV-1/2 Plus (Dade Behring, Marburg, Germany), an ELISA for the detection of antibodies to HIV-1, HIV-2 and HIV-1 (subtype Selleck PLX3397 O) antigens. Plasma from all ELISA-negative samples were batched and tested using the pooled NAAT strategy [5,6]. Each master pool
comprised 10 samples, consisting of 100 μL from each sample to a total volume of 1000 μL, and tested with qualitative HIV-1 RNA polymerase chain reaction (PCR) assay (COBAS Amplicor™ System, Roche Molecular Systems; Systems, Inc., Branchburg, New Jersey, USA). Master pools testing negative were considered HIV-negative with no further testing. If any of the master pools tested positive for HIV-1 RNA, quantitative testing was performed on individual samples using the COBAS AmpliPrep/COBAS TaqMan (Roche Molecular Systems) which has a detection level of ≥40 HIV-1 RNA copies/mL. HIV antibody-negative samples with detectable plasma
HIV-1 RNA were retested using the third-generation Abbott Determine HIV-1/2 rapid antibody test (Abbott Laboratories). We calculated RG7204 the cost of HIV-1 RNA testing by including the cost of consumables, test kits and technicians’ time. AHI was defined as HIV ELISA antibody-negative, qualitative HIV-1 RNA-positive with measurable HIV-1 RNA copies/mL. The proportion of women with AHI was calculated by dividing the number of women who were HIV-1 RNA-positive by the total number of ELISA-negative samples tested. The annual HIV incidence was calculated using the formula I=(365/w)Ninc/(number at risk), where I is the incidence rate and w is the mean window of detection (28 days). Ninc is the number of women found to be HIV-1 RNA-positive. The denominator, number at risk, is the number of HIV ELISA seronegative women tested. The HIV incidence is reported as a percentage per year. The 95% confidence interval (CI) for the incidence estimate was calculated using±1.96 [5,6]. The Biomedical Research Ethics Committee of the
University of KwaZulu-Natal and the uMgungundlovu District KwaZulu-Natal Department of Health approved the study. A total of 750 consecutive samples were collected from pregnant women during their first antenatal care visit. Farnesyltransferase The HIV prevalence at screening, patient demographics and HIV test characteristics are shown in Table 1. The overall HIV prevalence was 37.3% (95% CI 34.3–41.3]. Of the 467 ELISA HIV antibody-negative samples, four (0.9%) tested HIV-1 RNA-positive and antibody-negative with the Abbott Determine rapid assay. The mean viral load was 386 260 copies/mL (range 64 200–1 228 130). Based on the HIV-1 RNA-positive samples, the point estimate of HIV incidence was 11.2% per year (95% CI 0.3–22.1). All women diagnosed with AHI were ≤21 years of age. The ages of the current partner for two women were <25 years and, for the other two, >25 years. Only one woman reported a history of a previous pregnancy. The mean ages of women without AHI and their current partner were 22.