ANONYMOUS TESTING OF NEWBORN-INFANTS FOR HIV ANTIBODIES AS A BASIS FOR ESTIMATING PREVALENCE OF HIV IN CHILDBEARING WOMEN - THE 1991-1994 STUDY IN SPAIN

During 1991-1994, anonymous screening of newborn infants for maternal antibody to human immunodeficiency virus (HIV) was carried out in thre e regions of Spain: Valencia, Galicia and Sevilla. The newborn infants whose heel-stick blood eluates were satisfactory for HIV antibody tes ts were a consecutive series of 104 876, representing 99.3% of all new born infants undergoing routine metabolic screening and estimated as c omprising at least 98% of all births in the three regions. Enzyme immu noassay (EIA) positives were confirmed by immunoblot, yielding 246 con firmations: a rate of 2.3 per 1000. Seropositivity rates ranged from 1 .4 per 1000 in Galicia to 2.1 in Sevilla and 3.1 in Valencia, and rema ined relatively stable in each region during the years of the study. W ithin socioeconomically defined subgroups of birth hospitals in Valenc ia and Galicia, all subgroups contained seropositives, even though the re was a twofold to fivefold over-representation in the ''inner city'' public hospitals. To estimate the proportion of HIV-1-seropositive ne wborn infants who were positive for HIV-1 DNA, polymerase chain reacti on (PCR) assays were performed on 165 dried blood spots that had been retained following positive immunoblot assays. Fifteen (9%) were PCR p ositive, and when this proportion is adjusted for the age-specific sen sitivity of the method, it translates into an estimated HIV-1 transmis sion rate of 24% (range 18-36%). For 94 906 of the 104 876 newborn inf ants screened, the EIA used could detect antibodies that react with ep itopes of HIV-1 and HIV-2. Then were 30 newborn infants whose blood el uate was positive by this combined HIV-1/HIV-2 antibody screen and who se secondary screening with monovalent HIV-2 and HIV-1 EIA indicated t hat the HIV-2 reactivity was above the cut-off whereas the HIV-1 was n ot. Ranking these 30 results according to absolute HIV-2 reactivity an d relative reactivity with respect to HIV-1 indicated that four infant s were probable true HIV-2 seropositives and a total of 12 were possib le HIV-2 seropositives, a prevalence of the order of 1:10000 to 1:2000 0 newborn infants. These anonymous population-based serological studie s provide ''leading-indicator'' data to complement traditional AIDS su rveillance for epidemiological and planning purposes.