HIV infection can be definitively diagnosed through the use of viral diagnostic assays in most infected infants by age 1 month and in virtually all infected infants by age 6 months. Tests for antibodies to HIV, including newer rapid tests, do not establish the presence of HIV infection in infants because of transfer of maternal antibodies; therefore a virologic test should be utilized [10].
A positive virologic test (i.e., detection of HIV by culture, DNA polymerase chain reaction [PCR] or RNA assays) indicates possible HIV infection and should be confirmed by a repeat virologic test on a second specimen as soon as possible after the results of the first test become available. Diagnostic testing should be performed before the infant is age 48 hours, at age 1–2 months, and at age 3–6 months. Additional testing at age 14 days might allow for early detection of infection.
HIV infection is diagnosed by two positive HIV virologic tests performed on separate blood samples, regardless of age.
HIV DNA PCR is the preferred virologic method for diagnosing HIV infection during infancy. A meta-analysis of published data from 271 infected children indicated that HIV DNA PCR was sensitive for the diagnosis of HIV infection during the neonatal period. Thirty-eight percent (90% confidence interval [CI] = 29%–46%) of infected children had positive HIV DNA PCR tests by age 48 hours [17]. No substantial change in sensitivity during the first week of life was observed, but sensitivity increased rapidly during the second week, with 93% of infected children (90% CI = 76%–97%) testing positive by PCR by age 14 days. By age 28 days, HIV DNA PCR has 96% sensitivity and 99% specificity to identify HIV proviral DNA in peripheral blood mononuclear cells (PBMCs) [16].