Rapid and precise quantification of HIV-1 RNA in plasma using a branched DNA signal amplification assay

The branched DNA (bDNA) signal amplification assay may be useful in measuring blood levels of HIV RNA during HIV infection. This assay uses nucleotide probes attached to a microwell that bind to viral RNA in blood samples placed in the well. Researchers used the assay to measure HIV RNA in blood samples from 349 HIV-positive people. The assay detected HIV RNA in 83% of the patients with CD4 T cell counts less than 500. HIV RNA levels rose as the number of CD4 T cells dropped. However, RNA levels remained stable in patients with stable disease. HIV RNA levels initially dropped in one patient on long-term AZT therapy, but began to rise again 19 weeks after treatment began. This indicates that the drug was no longer effective, even though the patient's CD4 counts remained stable. This assay could be useful in documenting a patient's response to treatment.