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HIV Viral Load

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Also known as: HIV Nucleic Acid Amplification Test; HIV NAAT; HIV NAT; HIV PCR; HIV RNA Test; HIV Quantification
Formal name: Human Immunodeficiency Virus RNA, Quantitative
Related tests: CD4 Count; HIV Antibody and HIV Antigen (p24); HIV Drug Resistance (Genotypic and Phenotypic)

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The Test Sample

What is being tested?

Human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS). This test measures the amount (viral load) of HIV genetic material (RNA) in the blood.

When a person is initially infected with HIV, the virus replicates — it produces more and more copies of itself. The main target of HIV is the CD4 cells, which are a type of white blood cell that fights infections. The virus enters the cells and uses them to replicate and spread throughout the body. It 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. Without treatment and even when there are no symptoms, the virus continues to replicate and the viral load will increase. HIV kills CD4 cells, so the number of CD4 cells will decrease as HIV infection progresses.

About 3-8 weeks after initial exposure to the virus, the person's immune system begins to produce HIV antibodies in response to the infection and suppresses the HIV viral load, decreasing it to a low level. Initial symptoms typically resolve, but the infection does not go away.

The only way to determine whether a person has been infected is through HIV testing. If not detected early and treated, an HIV infection may slowly degrade the immune system. After several years and without treatment, the immune system can become so weakened that the disease begins to affect the body's ability to fight infections and certain cancers. Symptoms of AIDS 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.

When a person is diagnosed, antiretroviral treatments for HIV (also called highly active antiretroviral therapy or HAART) are initiated to suppress the amount of HIV virus present in the blood, limiting its ability to replicate and reducing the risk of progressing to AIDS. If a person with HIV discontinues treatment or if it loses its efficacy, then the person's HIV viral load can begin to increase again.

The HIV RNA test detects HIV virus genetic material and measures how many copies of HIV (viral load) are present in the blood at a particular time. It can track increases and decreases in HIV viral load and, in conjunction with a CD4 count, be used to evaluate treatment effectiveness.

How is the sample collected for testing?

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