The gold standard test for HIV infection in infancy was HIV DNA PCR on peripheral blood lymphocytes. Cyclopamine In a number of studies, including the large French perinatal cohort, equal or increased early sensitivity with amplification of viral RNA with no false positives
has been reported [330, 331]. Infants infected intrapartum may have low peripheral blood HIV levels, so HIV DNA/RNA may not be amplified from all infected infants at birth. Indeed a positive HIV DNA/RNA result within 72 hours of birth is taken as presumptive evidence of intrauterine transmission. Within the first few weeks of life the sensitivity of the viral diagnostic tests increases dramatically and by 3 months of age 100% of non-breastfed HIV-positive infants are likely to be detected [331]. Although HIV RNA and DNA assays have similar sensitivity, RNA assays commonly require 1 mL of plasma. If the sample requires dilution due to a low volume, which is often the case with paediatric samples, the AG 14699 lower limit of detection will be increased (with a corresponding decrease in assay sensitivity). Ideally, the lower limit of detection should not exceed 100 copies/mL following dilution. In addition where MTCT may have occurred
in utero, subsequent maternal antiretroviral therapy with agents that cross the placenta could lead to a false-negative RNA result in an infected infant. This risk would be highest in a late-presenting mother. In this situation the infant should be tested using DNA PCR. The same considerations regarding using primers known to amplify maternal virus apply to
both RNA and DNA assays. In view of the genomic diversity of HIV, a maternal sample should always be obtained for HIV DNA or RNA amplification with, or prior to, the first infant sample to confirm that the primers Protein kinase N1 used detect the maternal virus. If the maternal virus cannot be detected then a different primer set and/or test should be used. There has been an increase in the number of cases, usually mothers established on antiretroviral therapy long term with fully suppressed HIV, where it has not been possible to amplify maternal DNA using four different primer sets. HIV DNA/RNA results on their infants should therefore be interpreted with caution and in the light of clinical and serological findings. Infant HIV diagnostic testing should be undertaken at birth, 6 weeks and 12 weeks of age. Evidence from the French perinatal cohort demonstrated that neonatal ART, especially if more than one drug, can delay the detection of both HIV DNA and RNA in the infant [332]. For this reason, the second and third HIV molecular tests are performed at 2 weeks and 2 months after stopping PEP, i.e. usually at 6 weeks and 12 weeks of age.