Human immunodeficiency virus type 1 (HIV-1) RNA can be measured using qualitative or quantitative techniques. Qualitative testing (commonly referred to as nucleic acid testing or NAT) is used as a screening test to identify HIV infected individuals, such as screening possible blood donors. Quantification of HIV-RNA (viral load measurements) can be used as a diagnostic test in certain situations; however, the HIV viral load is primarily used for management/monitoring of HIV-1 infected individuals.
This topic will address the laboratory methods for quantitation of HIV-1 RNA and the use of viral load for clinical management. Information on nucleic acid, HIV-2 RNA, and CD-4 cell count testing is found elsewhere. (See "Blood donor screening: Laboratory testing", section on 'HIV-1 and HIV-2' and "Clinical manifestations and diagnosis of HIV-2 infection", section on 'Testing for HIV-2 infection' and "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-naïve HIV-infected patient" and "Patient monitoring during HIV antiretroviral therapy".)
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.
LABORATORY METHODS FOR QUANTITATION OF HIV-1 RNA
There are four commercial assays that have been approved by the United States Food and Drug Administration (FDA) to quantify HIV-1 RNA from plasma samples: