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HIV Viral Load

Also known as: Nucleic acid amplification test (NAAT); NAT; HIV PCR; Quantitative plasma RNA test; HIV Quantification
Formal name: Human Immunodeficiency Virus RNA quantitative
Related tests: CD4 and CD8; HIV antibody; HIV Proviral DNA; p24 antigen test; HIV drug resistance (genotypic and phenotypic)

At a Glance

Why Get Tested?

To monitor the status of HIV disease, in conjunction with other lab tests and physical disease progression, and to guide therapy

When to Get Tested?

When first diagnosed with HIV, every 2 to 8 weeks at the start of therapy or therapy changes, and every 3 to 4 months during long-term therapy, or as your doctor recommends

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

This test detects and/or measures the amount (viral load) of RNA (nucleic acid) of the human immunodeficiency virus (HIV) in blood. It is the virus that causes acquired immunodeficiency syndrome (AIDS). When a person is infected with HIV, the virus replicates — it produces more and more copies of itself — and moves into the lymph nodes, spleen, and other parts of the body. In the early stages of infection, there may not be any noticeable signs or symptoms of disease or only flu-like symptoms, although the virus is usually present in high amounts. Even when there are no symptoms, the virus continues to replicate and to damage or kill immune cells. Eventually, the immune system is so weakened that the disease begins to affect the body’s ability to fight infections and certain cancers. More symptoms begin to appear at this stage as the body becomes more susceptible to infections with microorganisms such as tuberculosis and fungi or other diseases such as Kaposi’s sarcoma.

About 3-8 weeks (rarely up to six months) after exposure to the virus, the body begins to produce HIV antibodies in response to the infection. These antibodies can be detected with a screening test to determine if you have been infected with HIV. However, if your exposure occurred within the last few weeks, the level of antibody may not be high enough to be detected. It is in this “window period” of more recent exposure that the virus may be detectable with an HIV RNA test (viral load) to determine your HIV status. Because the level of technology and resources needed to perform this test are high, it is not as widely available as the antibody test and is used infrequently for diagnosis. Occasionally, a p24 antigen test is used to detect early infection with HIV.

As HIV progresses, the virus continues to replicate and the number of copies of virus, the “viral load,” in the blood increases. If you have been diagnosed with HIV, the measurement of an HIV viral load (HIV RNA) gives your doctor a general indication of how much HIV is present in the body and how rapidly the virus is replicating. The test can help determine, along with a CD4 count, if and when treatment should be initiated, when to test for drug resistance, or if a different type of treatment protocol is needed. Treatment with anti-viral agents can decrease the viral load in the blood to low or undetectable levels but cannot fully eradicate it from the body.

How is the sample collected for testing?

A blood sample is drawn by needle from a vein in your arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

The viral load test is a quantitative measurement of HIV nucleic acid (RNA) that provides important information that is used in conjunction with the CD4 cell count:

  • to monitor the status of HIV disease,
  • to guide recommendations for therapy, and
  • to predict the future course of HIV.

Evidence shows that keeping the viral load levels as low as possible for as long as possible decreases the complications of HIV disease, slows the progression from HIV infection to AIDS, and prolongs life.

There are several methods for testing viral load; results are not interchangeable so it is important that the same method be used each time.

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When is it ordered?

An HIV viral load test is ordered when a patient is first diagnosed with HIV. It is usually ordered in conjunction with a CD4 count. The test results function as a baseline measurement that shows how actively the virus is reproducing and whether treatment is immediately necessary.

If and when therapy is started, your doctor will usually order a viral load test and a CD4 count about two to eight weeks after you start a treatment to evaluate whether therapy is being effective. To monitor long-term therapy, your doctor will order viral load tests and CD4 counts about every three to four months.

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What does the test result mean?

HIV viral load tests are reported as the number of HIV copies in a milliliter (copies/mL) of blood. If the viral load measurement is high, it indicates that HIV is reproducing and that the disease will likely progress faster than if the viral load is low. During treatment and monitoring, a high viral load can be anywhere from 5,000 to 10,000 copies/mL. Initial, untreated, and uncontrolled HIV viral loads can range as high as one million or more copies/mL. A low viral load is usually between 40 to 500 copies/mL, depending on the type of test used. This result indicates that HIV is not actively reproducing and that the risk of disease progression is low.

A viral load result that reads “undetectable” does not mean that you are cured. It may mean that either the HIV RNA is not present in your blood at the time of testing or that the level of HIV RNA is below the threshold needed for detection. Even though HIV may be undetectable in the blood, it persists in cells and tissues throughout the body as “HIV provirus.” HIV provirus refers to virus that has moved into cells and into the nucleus, where it has become integrated with the DNA of the host cell. This is also call “HIV proviral DNA.”

If you are not taking your medication as your physician has directed, your viral load may not drop as significantly as if you take your medication on time.

Change in viral load is also a very important measurement. A rising count indicates either that the infection is getting worse or that you have developed resistance to the drugs that are being used for therapy, while a falling count indicates improvement and suppression of the HIV infection.

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Is there anything else I should know?

The HIV viral load test is used for monitoring the level of virus after the initial diagnosis of HIV. In general, the HIV antibody test is the recommended method of choice for the diagnosis of HIV.

HIV viral load testing done by the PCR method is exceptionally sensitive, which can give rise to some false-positive results.

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Common Questions

1.  Will exercise, nutrition, and other lifestyle modifications help decrease my viral load levels?

There is no direct link between viral load levels and exercise, nutrition, or other lifestyle factors. However, the CDC does suggest that if you eat healthy foods, you will stay strong and keep up your energy. This and more information is contained in the CDC brochure Living with HIV.

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2.  I know that an HIV viral load test detects HIV RNA. What is an HIV DNA test?

The HIV DNA test, also call HIV Proviral DNA test, is a qualitative test for HIV used to screen for infection in infants born to HIV-infected mothers. It may be used to help diagnose HIV within the one to three weeks time period (or sometimes up to six months) after birth.

This test is performed in babies because antibodies to HIV produced by the mother can cross the placenta and enter the baby’s blood. The result of the baby’s antibody test could be positive even though he is not infected with the virus. After infection, the virus enters the cell and replicates. The viral particles enter the nucleus of the cell and integrate with the DNA of the cell. This HIV proviral DNA now becomes a permanent part of the host cell. That is why even if your viral load is undetectable, you are not cured and the virus will still be present in the cell.

The immune system in babies is immature and, if they are infected by the mother at birth, there is not enough virus in the blood that is detectable. However, if the baby has been exposed to the virus, the integrated proviral DNA will be present and can be detected. An infant with a positive HIV DNA test is infected with the virus, while a negative HIV DNA test means that the baby is not infected (or may have been tested too soon after birth).

Babies born to mothers infected with HIV may be tested soon after birth with an HIV DNA test. If negative, the test may be repeated when the infant is 1 to 2 months old and again at 3 to 6 months old. This may be necessary as the amount of virus may not be at a detectible level.

If HIV DNA is positive, follow up tests such as a CD4 cell count and viral load may identify babies that could benefit from early treatment.

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp. 535-538.

Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Pp. 487-490.

Bennett, N. and Rose, F. (2008 October 22, Updated). HIV Disease. eMedicine [On-line information]. Available online at http://www.emedicine.com/med/TOPIC24.HTM through http://www.emedicine.com. Accessed on 10/26/08.

Mayo Clinic Staff (2008 August 9). MayoClinic HIV/AIDS. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/hiv-aids/DS00005 through http://www.mayoclinic.com. Accessed on 10/30/08.

(2005 November, Revised). Human Immunodeficiency Virus (HIV) Introduction. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec14/ch192/ch192a.html?qt=HIV&alt=sh through http://www.merck.com. Accessed on 10/30/08.

(2008 September, Reviewed). Human Immunodeficiency Virus – HIV. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/InfectiousDz/Viruses/HIV.html through http://www.arupconsult.com. Accessed on 10/30/08.

(2006 September 22). Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings. CDC MMWR 55(RR14); 1-17 [On-line information]. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5514a1.htm through http://www.cdc.gov. Accessed on 11/1/08.

(2008 September, Updated) HIV and Plasma Viral Load Testing. Familydoctor.org [On-line information]. Available online at http://familydoctor.org/online/famdocen/home/common/sexinfections/hiv/654.html through http://familydoctor.org. Accessed on 11/1/08.

(Updated January 9,2009) AVERT.org. HIV testing. Available online at http://www.avert.org/testing.htm. Accessed February 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006, Pp. 1567-1568.

(October 22, 2007) National Institute of Allergy and Infectious Diseases. HIV/AIDS. Available online at http://www3.niaid.nih.gov/topics/HIVAIDS/. Accessed February 2009.

Arup Laboratories. ArupConsult. Human Immunodeficiency Testing in Infants. PDF available for download at http://www.arupconsult.com/Algorithms/HIVInfants.pdf through http://www.arupconsult.com. Accessed February 2009.

Henry’s Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, P. 989.

(Reviewed Oct 7, 2008) AIDS infonet.org. Fact sheet, Viral Load Tests. Available online at http://www.aidsinfonet.org/fact_sheets/view/125 through http://www.aidsinfonet.org. Accessed February 2009.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Janice K. Pinson MT, MBA. Molecular Business Strategies, Birmingham, MI.