Early diagnosis of HIV-1-infected infants in Thailand using RNA and DNA PCR assays sensitive to non-B subtypes.

The aim was to evaluate the sensitivity and specificity of RNA and DNA polymerase chain reaction (PCR) for early diagnosis of perinatal HIV-1 infection and to investigate early viral dynamics in infected infants. A cohort study of 395 non-breast-fed infants born to HIV-infected mothers was conducted in a randomized clinical trial of short-course antenatal zidovudine. Infant venous blood specimens collected at birth 2 months and 6 months of age were tested by qualitative DNA and quantitative RNA PCR (Roche Amplicor). To determine sensitivity and specificity of DNA and RNA PCR results were compared with later DNA PCR results and to antibody results at 18 months. The HIV-1 subtype of the mothers infection was determined by peptide serotyping. In the study 92% of mothers were infected with subtype E. DNA PCR sensitivity was 38% (20 of 53) at birth and 100% at 2 months (53 of 53) and 6 months (47 of 47). RNA PCR sensitivity was 47% (25 of 53) at birth and 100% (53 of 53) at 2 months. All samples that tested DNA-positive tested RNA-positive. Specificity was 100% for both DNA and RNA testing at all timepoints. For infected infants the median viral load of RNA-positive specimens was 407000 copies/ml (5.6 log 10) at birth 3700000 copies/ml (6.6 log 10) at 2 months and 1700000 copies/ml (6.2 log 10) at 6 months. Infant RNA levels at 2 and 6 months did not differ by maternal zidovudine exposure or RNA level at birth. This RNA PCR assay performed well for diagnosing perinatal HIV subtype E infection detecting nearly half of infected infants at birth and 100% at 2 and 6 months with 100% specificity. Infected infant viral RNA levels were very high at 2 and 6 months and were unaffected by maternal zidovudine treatment. (authors)