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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