Back Blood-tests Explained
HIV Viral Load
At a Glance
Why Get Tested?
If you have been diagnosed with human immunodeficiency virus (HIV), initially to determine the status of the infection and subsequently to monitor the effectiveness of antiretroviral treatment
When to Get Tested?
When first diagnosed with HIV; 2 to 8 weeks after the start of therapy or therapy changes, then every 4 to 8 weeks until the viral load is not detectable; then every 3 to 4 months if you are on stable therapy and the virus remains suppressed; after two years of this, viral load testing frequency may be decreased to every 6 months.
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
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.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
The Test
How is it used?
The HIV viral load test is used initially, along with a CD4 count, to determine the status of HIV infection in a person diagnosed with the disease. The viral load is then used to monitor the effectiveness of antiretroviral treatment (ART) over time. Photo source: CDC / A. Harrison, P. Feorino
HIV viral load testing measures the amount of HIV genetic material (RNA) in the blood and reports how many copies of the virus are present. Evidence shows that keeping the viral load at undetectable levels decreases an infected person's risk of progressing to AIDS and greatly improves long-term health.
It is recommended that all individuals diagnosed with HIV infection receive antiretroviral treatment as soon as possible, including pregnant women. People typically take at least three drugs from two different classes in order to prevent or minimize virus replication and the emergence of drug-resistant strains. Combinations of three or more antiretroviral drugs are referred to as highly active antiretroviral therapy or HAART.
The HIV viral load may also be used to help determine whether the virus infecting a person has become drug-resistant. If a person does not respond well to treatment and the amount of virus continues to increase, then the virus may be resistant to that particular ART. The person's treatment will then likely be modified.
HIV viral load tests are most useful when they are compared with results obtained from earlier tests. They are used in combination with the CD4 count to monitor how effective ART is in suppressing the virus. CD4 cells are types of white blood cells that fight infection and play an important role in immune system function. They are the main target of HIV. The virus enters the cells and uses them to make copies of itself (replicate) and spread throughout the body. HIV kills CD4 cells as it replicates. If HIV is not detected early and treated, the viral load will increase and the number of CD4 cells will decrease.
When is it ordered?
An HIV viral load test is typically ordered with a CD4 count when a person is first diagnosed with HIV infection as part of a baseline measurement. After the baseline, a viral load test will usually be ordered at intervals over time, depending on a few different factors.
The following table summarizes recommendations* for the timing of viral load testing and CD4 counts:
| Clinical Status of Patient | Viral Load | CD4 Count |
| When first diagnosed | Test performed | Test performed |
| After initiating ART | Within 2-4 weeks and then every 4-8 weeks until virus is suppressed (undetectable) | 3 months later |
| During the first 2 years of stable ART | Every 3-4 months | Every 3-6 months |
| After 2 years of stable ART, virus undetectable, and CD4 greater than 300 cells/mm3 | Can extend to every 6 months | Annually; if CD4 consistently greater than 500 cells/mm3, monitoring is optional |
| After changing ART due to side effects or simplifying drug regimen in a person with suppressed virus | After 4-8 weeks, to confirm drug effectiveness | Monitor according to prior CD4 count and the amount of time person has been on ART, as detailed above |
| After changing ART due to increased viral load (treatment failure) | Within 2-4 weeks and then every 4-8 weeks until virus undetectable | Every 3-6 months |
| While on ART and viral load is consistently greater than 200 copies/mL | Every 3 months | Every 3-6 months |
| With new HIV symptoms or start of new treatment with interferon, corticosteroids or cancer drugs | Every 3 months | Perform test and monitor according to health status (e.g., new HIV symptoms, opportunistic infections) |
*Adapted from Guidelines for the Use of Antiretroviral Agents in HIV-1–Infected Adults and Adolescents, Table 4. Recommendations on the Indications and Frequency of Viral Load and CD4 Count Monitoring.
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 generally indicates that HIV is present and replicating. Initial, untreated, and uncontrolled HIV viral loads can range as high as one million or more copies/mL.
In someone who is receiving antiretroviral treatment (ART), a high viral load means that the treatment is not effective. People who do not respond to treatment will likely have their therapy changed. They should undergo HIV drug resistance testing to help in the selection of an alternative therapy.
Viral loads that are consistently less than 200 copies/mL indicate that the virus is adequately suppressed and that the risk of disease progression is low. Nevertheless, an undetectable viral load in someone who has a diagnosed HIV infection does not mean that the person is cured; it means only that the level of HIV RNA is currently below the threshold needed for detection by the test.
Changes in viral load can often be more important during HIV monitoring than a single test result. An increasing viral load indicates either that the infection is getting worse or that the virus has developed resistance to the drugs that are being used for therapy and are no longer effective. A decreasing viral load indicates improvement, treatment effectiveness, and suppression of the HIV infection.
Is there anything else I should know?
Even when HIV is 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 the nucleus of cells and has become integrated with the DNA of the host cell. This is also called "HIV proviral DNA."
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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