Prevalence of indeterminate human immunodeficiency virus western blot results in pregnant women attended at a public hospital in Presidente Prudente, Brazil.

The AIDS epidemic is spreading rapidly among women worldwide, offering increasing opportunities for vertical transmission of HIV. In Brazil, the prevalence of HIV infection among pregnant women is less than 1%. Therefore, the positive predictive value of an HIV EIA test tends to be lower than the more frequent indeterminate Western blot result. Pregnant women receiving antenatal care, from 2000 to 2004, at a public secondary hospital in the city of Presidente Prudente, São Paulo, Brazil, were systematically screened for HIV by means of two distinct EIA tests, in order to determine the prevalence of indeterminate Western blot results among pregnant women showing discordance in both HIV EIA tests and indirect immunofluorescence assay. Confirmatory indirect immunofluorescence was performed on material for all women with positive results in both EIA tests. Whenever there were positive results in EIA and IIA, the applicant was retested by the initial screening assay. Only those not showing concordance in results in EIA and IAA had a Western blot performed. The viral load was measured in pregnant women with positive or indeterminate Western blot results. Out of 9,786 sera, 105 (1.0%) were positive in the two HIV EIA screening tests, confirmed by indirect immunofluorescence. Among these women, Western blot was interpreted as indeterminate in 11 (0.1%) cases and their viral load was <50 copies/mL. We found a prevalence of 0.1% HIV indeterminate Western blots in pregnant women from Presidente Prudente and the surrounding region; none of these pregnant women had positive HIV viral loads.