The Use of Viral Culture and p24 Antigen Testing to Diagnose Human Immunodeficiency Virus Infection in Neonates

BACKGROUND: Early diagnosis of human immunodeficiency virus (HIV) infection in infants born to infected mothers is important for the infants' medical care, but the presence of maternal antibodies makes serologic tests uninformative. METHODS: In a cohort study of 181 infants born to HIV-infected mothers, we assessed the diagnostic value of HIV viral culture and testing for the presence of p24 antigen. The infants were tested at birth, again during the first 3 months, then followed and tested at the age of at least 18 months. RESULTS: Of the 181 infants, 3 died of HIV infection and 37 were seropositive after the age of 18 months. Viral cultures at birth were positive in 19 of the 40 infected infants and in none of the uninfected infants, yielding a sensitivity of 48 percent (95 percent confidence interval, 32 to 63 percent) and a specificity of 100 percent (95 percent confidence interval, 97 to 100 percent). By the age of three months, 30 of the 40 infants (75 percent) had positive cultures; again, there were no false positive results among the infants who were tested a second time, of the 141 who remained uninfected. The sensitivity of testing for p24 antigen at birth was only 18 percent, with a specificity of 100 percent. The presence of p24 antigen at birth was associated with the development of early and severe HIV-related disease (P less than 0.04). CONCLUSIONS: Viral culture at birth can correctly identify about half of newborns with HIV infection. The fact that this usually sensitive technique fails to identify about half the ultimately infected neonates suggests that vertical transmission of HIV may occur late in pregnancy or during delivery.