Test Code: 902581


Clinical Use

  • Assess prognosis
  • Monitor progression of HIV infection and determine when to initiate therapy
  • Monitor effect of antiretroviral drug therapy

Clinical Background

Measurement of HIV-1 RNA plasma levels (viral load) provides a direct assessment of viremia and should be used in conjunction with CD4+ T-cell counts. The baseline (pre-treatment) HIV RNA level, combined with the baseline number of CD4+ T cells, predicts progression to AIDS and death.1,2 Periodic viral load assessment can be used to track the actual progression of the infection and is an essential parameter for determining when to initiate therapy. Once therapy has begun, HIV-1 RNA levels provide important information regarding therapeutic response. Following initiation or change in antiviral regimen, responders show a rapid decline in viral load by 2–8 weeks and a maximum antiviral effect on HIV RNA in 4-5 months.3 The goal is an approximate 1.0 log10 reduction within 2-8 weeks and a decline to <50 copies/mL by 16-20 weeks.3 Optimally, levels <50 copies/mL will be sustained 6 or more months. In multiple studies, decreases in viral load have been correlated with improved clinical outcome (i.e., survival). Such correlation was independent of pretreatment HIV RNA levels, baseline CD4+ T cells, and prior drug experience. Thus, HIV viral load is essential for treatment optimization and should be used to assess therapeutic response and when making changes in therapy.

Measurement of the HIV-1 RNA level and the CD4+ T-cell count is recommended at the following times:

  1. At the time of diagnosis
  2. Every 3-4 months for HIV-1 RNA or every 3-6 months for CD4+ T-cell count to monitor progression in untreated patients
  3. On two occasions immediately prior to initiation of therapy; 2 measurements, 2-4 weeks apart
  4. 3-4 weeks after initiating or changing therapy
  5. Every 3-4 months thereafter to monitor continuing effectiveness of therapy.3 
  6. More frequently as critical decision points are neared, such as the return of the viral load to baseline values.

If levels are still detectable after 16-20 weeks of therapy, the HIV RNA measurement should be repeated for confirmation, using a second sample, prior to changing therapy.3 Do not perform HIV RNA testing within four weeks of immunization or resolution of intercurrent infections.3


Individuals Suitable For Testing

  • Individuals recently diagnosed with HIV infection
  • Individuals in the clinically latent period of the infection
  • Individuals undergoing antiretroviral therapy
  • This test is not intended for use as a screening test or as a diagnostic test to confirm the presence of HIV-1 infection.

Specimen Requirements

Collect 4-6 mL whole blood in an EDTA lavender-top tube or PPT white-top tube, centrifuge within 6 hours of collection, and transfer plasma to a plastic vial prior to freezing. Plasma must be stored and transported frozen. Frozen PPT white-top tubes and frozen plasma from a yellow-top ACD tube are not acceptable.


CPT Code*

87536


Method

  • Reverse transcription of HIV-1 RNA to produce complementary DNA (cDNA)
  • Simultaneous PCR amplification of target cDNA and detection of fluorescent-labeled probes specific to the target
  • The earlier in the amplification process that fluorescence is detected, the higher the virus concentration in the sample
  • Reportable range: 48 - 10,000,000 Copies/mL (one copy of HIV-1 RNA is equivalent to 1.7 International Units (IU) based on the WHO International Standard for HIV-1)
  • Specificity: Group M, Subtypes (clades) A through H
  • Synonyms: Human Immunodeficiency Virus-1 (HIV-1) Viral Load

Values obtained from different vendor methods are not interchangeable due to variations in reagent specificity and other methodological differences. The use of one method when monitoring patients is recommended. If the methodology is changed, re-baselining is highly recommended prior to making clinical decisions.


Reference Range

48 - 10,000,000 Copies/mL or 1.68 - 7.00 LogCopies/mL


Interpretive Information

Initiation of therapy should be considered in asymptomatic patients having a PCR HIV-1 RNA level >20,000 copies/mL. When the PCR level is <20,000 copies/mL and the CD4+ T-cell count is >500/mm3, many experts forgo therapy, while others treat.4

A 5-fold (0.7 log10) change in HIV-1 RNA viral load is considered clinically significant.5 Increasing levels may be due to disease progression, failed antiretroviral therapy, other active infections (e.g., TB, pneumococcal pneumonia), or immunization. Decreasing levels indicate therapeutic response and improved outcome.


References

  1. Mellors JW, Munoz, A, Giorgi JV, et al. Plasma viral load and CD4+ lymphocytes as prognostic markers of HIV-1 infection. Ann Intern Med. 1997; 126:946-954.
  2. Mofenson LM, Korelitz J, Meyer WA III, et al, for the National Institute of Child Health and Human Development Intravenous Immunoglobulin Clinical Trial Study Group. The relationship between serum human immunodeficiency virus type 1 (HIV-1) RNA level, CD4 lymphocyte percent, and long-term mortality risk in HIV-1 infected children. J Infect Dis. 1997; 175:1029-1038.
  3. Guidelines for the use of antiretroviral agents in HIV- infected adults and adolescents. Use of testing for plasma HIV RNA levels and CD4+ T cell count in guiding decisions for therapy. [HIV/AIDS Treatment Information Service (ATIS) Web site]. April 23, 2001. Available at: http://www.hivatis.org/guidelines/adult/Apr23_01/text/testing.html. Accessed May 23, 2001
  4. Feinberg J, Maenza J. Primary Medical Care. In: A Guide to the Clinical Care of Women with HIV, 1st ed. [HIV/AIDS Bureau, Health Resources and Services Administration (HRSA) Web site]. 2001:77-138. Available at:  http://www.hab.hrsa.gov/publications/hrsawomen/chapter4/chapter4.htm. Accessed on March 15, 2002.
  5. Brambilla D, Reichelderfer PS, Bremer JW, et al. The contribution of assay variation and biological variation to the total variability of plasma HIV-1 RNA measurements. AIDS. 1999; 13:2269-2279.

*The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.

Polymerase Chain Reaction (PCR) is performed pursuant to a license agreement with Roche Molecular Systems, Inc.

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