Human immunodeficiency virus type 1 (HIV-1) RNA quantification or viral load measurements are routinely used in the management of persons infected with HIV-1.
This topic will address the methods used for HIV RNA detection and the use of viral load testing in clinical management. Information on the use of immunologic markers, such as CD4 cell counts, is found elsewhere. (See "Techniques and interpretation of measurement of the CD4 cell count in HIV-infected patients".)
IMPORTANCE OF HIV VIRAL LOAD MEASUREMENTS
Studies have shown HIV-1 RNA levels to be a predictor of the time to progression to acquired immunodeficiency syndrome (AIDS) and death that is independent of CD4 cell counts [1-6]. Viral load measurements are also useful in determining when to initiate antiretroviral therapy, and in monitoring the response to such therapy [7-11]. (See "Selecting antiretroviral regimens for the treatment naive HIV-infected patient".) In specific situations (neonatal infection and acute infection), HIV-1 RNA levels also may be useful in establishing the diagnosis of HIV infection, but HIV antibody tests are primarily used for this purpose. (See "Diagnostic assays for HIV infection".)
LABORATORY METHODS FOR QUANTITATION OF HIV-1 RNA
There are five commercial assays that have been approved by the United States Food and Drug Administration (FDA) to quantify HIV-1 RNA from plasma samples:
- The AMPLICOR HIV Monitor Test (Roche Diagnostics) is a conventional reverse transcriptase polymerase chain reaction (RT-PCR) assay  (standard and ultrasensitive)
- Versant HIV-1 RNA 3.0 assay (Bayer Diagnostics) is a branched DNA (bDNA) assay 
- The NucliSens HIV RNA QT (BioMereiux) is a nucleic acid sequence based amplification (NASBA) assay [14,15]
- The COBAS AmpliPrep/COBAS TaqMan HIV-1 Test (Roche Diagnostics) is a real-time RT-PCR assay .
- The RealTime HIV-1 (Abbott Molecular) is a real-time RT-PCR assay.