Techniques and interpretation of HIV-1 RNA quantitation
- Angela M Caliendo, MD, PhD
Angela M Caliendo, MD, PhD
- Executive Vice Chair of Medicine
- Brown University
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. Additional 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 found 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 an important factor in monitoring the response to such therapy . (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. However, in most other situations, combination tests that detect HIV p24 antigen and HIV antibodies are primarily used. (See "Screening and diagnostic testing for HIV infection", section on 'Tests'.)
LABORATORY METHODS FOR QUANTITATION OF HIV-1 RNA
Available tests — There are two real-time reverse transcriptase polymerase chain reaction (RT-PCR) commercial tests that are commonly used to quantify HIV-1 RNA from plasma samples:
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- IMPORTANCE OF HIV VIRAL LOAD MEASUREMENTS
- LABORATORY METHODS FOR QUANTITATION OF HIV-1 RNA
- Available tests
- Specimen collection
- Quantification and linear range
- Clinically significant changes in viral load
- Exogenous factors that may affect HIV RNA levels
- Relationship of HIV-1 RNA to CD4 cell count
- HIV-1 subtypes
- DIAGNOSTIC TESTING
- GUIDELINES FOR THE USE OF HIV-1 RNA LEVELS IN CLINICAL PRACTICE
- AVAILABILITY AND COST OF VIRAL LOAD TESTS
- SUMMARY AND RECOMMENDATIONS