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HIV-1 RNA, Quantitative bDNA (v3.0)

HIV-1 RNA, Quantitative bDNA (v3.0)

Test Summary

HIV-1 RNA, Quantitative bDNA (v3.0)


Clinical Use

  • Assess prognosis

  • Monitor progression of HIV-1 infection

  • Monitor effect of antiretroviral drug therapy

Clinical Background

Measurement of HIV-1 RNA plasma levels (viral load) provides quantitative measurement of viremia and is used in conjunction with CD4+ T-cell counts. The baseline (pre-treatment) HIV RNA level, combined with the baseline CD4 count, predicts progression to AIDS and death.1,2 Periodic viral load assessment is used to track progression of the infection and is the most important indicator of antiretroviral treatment response. Stable or increasing levels are associated with disease progression and/or treatment failure, whereas decreasing levels indicate therapeutic response. The primary goal of treatment is to decrease the viral load below detectable levels (<75 RNA copies/mL for this quantitative bDNA assay), which typically occurs within 12 to 24 weeks.3

Measurement of the HIV-1 RNA level and the CD4 count is recommended at the following intervals: 1) at entry into care; 2) every 3 to 6 months to monitor progression of HIV infection in untreated patients; 3) 2 to 8 weeks after initiation of therapy and every 4 to 8 weeks thereafter until the viral load is below detectable limits; 4) 2 to 8 weeks after changing therapy; and 5) every 6 to 12 months to monitor continuing effectiveness of therapy in stable patients unless new treatment with interferon, corticosteroids, or anti-neoplastic agents is initiated.3 HIV-1 RNA testing is generally not recommended within 4 weeks of immunization or resolution of intercurrent infections.

Individuals Suitable for Testing

  • Individuals recently diagnosed with HIV-1 infection

  • Individuals who are in the clinically latent period of the infection and not receiving antiretroviral therapy

  • Individuals receiving antiretroviral therapy


  • Capture and hybridization of RNA to HIV-1-specific probes and multiple branched DNA (bDNA) molecules

  • bDNA molecules hybridized to alkaline phosphatase-labeled probes

  • Chemiluminescent detection of bDNA molecules

  • Reportable range: 75 to 500,000 copies/mL4

  • Specificity: HIV-1 group M subtypes (clades) A through G4

  • Minimum detectable change in viral load: 0.51 log10 (across range of assay)4

  • Aliases: human immunodeficiency virus-1 (HIV-1) viral load

Values obtained from different methods (eg, bDNA, PCR) are not interchangeable due to variations in reagent specificity and other methodological differences. Use only one method when monitoring patients. If the methodology is changed, re-baselining is highly recommended prior to making clinical decisions.

Interpretive Information

A 3-fold (0.5 log10) change in HIV-1 RNA viral load is considered statistically significant.3 Increasing levels may be due to disease progression, failed antiretroviral therapy, suboptimal adherence to treatment, immunizations, or occasionally, other active infections (eg, tuberculosis, pneumococcal pneumonia). Decreasing levels indicate therapeutic response and improved clinical outcome.

In patients beginning treatment, persistent HIV RNA viremia at levels >200 copies/mL for more than 24 weeks indicates treatment failure.3 Patients with virologic failure (confirmed viral load >200 copies/mL) should be tested for antiretroviral drug resistance, which can be used to modify the treatment regimen.3


  1. Mellors JW, Phair JP, Rinaldo CR, et al. Prognostic value of HIV-1 RNA, CD4 cell count, and CD4 cell count slope for progression to AIDS and death in untreated HIV-1 infection. JAMA. 2007;297:2349-2350.

  2. Egger M, May M, Chene G, et al. Prognosis of HIV-1�infected patients starting highly active antiretroviral therapy: a collaborative analysis of prospective studies. Lancet. 2000;360:119-129.

  3. Panel on Antiretroviral Guidelines for Adults and Adolescents.Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents.Department of Health and Human Services. February 12, 2013. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Accessed May 1, 2013.

  4. Versant® HIV-1 RNA 3.0 assay (bDNA) [package insert]. Tarrytown, NY: Siemens Medical Solutions Diagnostics; 2008-07.

Content reviewed 07/2013

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