Viral Load and what it means
The plasma HIV-1 RNA PCR (aka viral load) is a measure of how much HIV virus there is in a person’s system.
It is mainly used for the monitoring of patients who are infected with HIV. However, in recent years, it has also found a role in early diagnosis of a HIV infection. This is discussed elsewhere. (Please do not post questions on using RNA PCR as a diagnostic tool in the comments section. You may post these questions on the other HIV articles.)
A high viral load has been associated with poor clinical progression and poor clinical outcome. In other words, a patient with a persistently high viral load is at higher risk of the CD4 count continuing to fall or fall faster leading to AIDS faster. They are also at a higher risk of kidney diseases, nerve problems and heart diseases related to HIV infection. This is one of the reasons why some doctors will still recommend ART even if the CD4 count is healthy.
The key indication of the viral load test is to monitor response to treatment. In other words, when we start a patient on ART, we want the viral load to go down and stay down. If the viral load does not go down or does not stay down, it means the medicines are not working. This can be due to several reasons like drug resistance, super infections or the patient just not taking his medicines as he/she should be doing.
Ideally, we want patients on treatment to have an undetectable viral load. With the current machines, this means a reading of < 20 copies/ml. This is usually achieved within 12 to 24 weeks of starting ART but can take longer in some patients. Do not be too surprised or disappointed if the viral load increases now and then. These are called isolated blips and they are not significant. If your viral load is persistently > 200 copies/ml, this might indicate a problem and you should discuss this with your doctor.
What to expect
Your doctor would almost definitely do a viral load test for you at the first visit.
A repeat viral load test will be done before you start ART and then repeated 2 to 4 weeks (not more than 8 weeks) after you start ART. This is to see how well the medicines are working. From then on, you will need repeat viral load tests at 4 to 8 weeks intervals until viral suppression is achieved.
The same regime described above also applies if you need to change ART medicines.
Once a patient has been stable for 2 to 3 years, viral load monitoring can be done every 3 to 6 months.
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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.