HIV Viral Load
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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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.
A blood sample drawn from a vein in your arm
Test Preparation Needed?
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.
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.
- Will exercise, nutrition, and other lifestyle modifications help decrease my HIV viral load?
There is no direct link between HIV viral load and exercise, nutrition, or other lifestyle factors. However, the Centers for Disease Control and Prevention (CDC) does suggest that if you eat healthy foods, you will stay strong and keep up your energy. More information about this is contained in the CDC brochure Living with HIV.
- If I have undetectable HIV viral load, can I still spread the disease?
Yes. Although having an undetectable viral load will decrease the chances of you spreading the disease to others, it can still happen. An undetectable viral load only means that there are too few copies of the virus present in the blood to be detected by the test. The virus can still be present in body fluids, such as semen and vaginal fluids, so you can still spread the virus if you have unprotected sex.
- Can an HIV RNA test be used to screen for HIV?
The recommended test for HIV screening is a combination test that detects HIV antibody and HIV antigen. By detecting both antibody and antigen, the combination test increases the likelihood that an infection is detected soon after exposure. Most HIV screening tests detect only HIV antibody but are good options for screening because they may be available as rapid tests and at the point of care. If any of these screening tests are positive, they must be followed by another different antibody test. If the second test is positive, then HIV diagnosis is confirmed. If however, the first and second result do not match, then an HIV RNA test may be done to help establish a diagnosis.
The recommended screening test for newborns, however, is an HIV RNA test (see Question 4).
- Why is the HIV RNA test used to test newborns for HIV infection?
Babies born to mothers infected with HIV are typically tested soon after birth (usually within one to four months) to help determine whether the mother has passed the infection to her baby. An HIV RNA test is performed in babies instead of standard screening HIV antibody tests because antibodies to HIV produced by the mother can cross the placenta and enter the baby's blood. If an HIV antibody test were to be performed on a baby, the result could be positive even though the baby is not infected with the virus.
An infant with a positive HIV RNA test is likely infected with the virus. Repeat testing done on a second blood specimen is done to confirm the diagnosis. A negative HIV RNA test means that the baby is not infected (or may have been tested too soon after birth). If negative, the test is usually repeated when the infant is older than 1 month and again when the baby is older than 4 months. This may be necessary as the amount of virus may not be at a detectable level.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.