HIV viral load measurement in HIV patients

To detect and quantify HIV virions in patients with a confirmed HIV infection, with the aim of predicting disease progression and monitoring antiretroviral therapy response. It is important to determine the viral load at specific time points and at frequent intervals in order to timely take corrective measures when needed, such as performing a drug resistance test, counselling adherence and changing antiretroviral therapy.

Viral load assays are molecular tests that amplify, detect and quantify either HIV-1 or HIV-2 RNA molecules by using HIV-1 or HIV-2 specific primers and/or probes.

Viral load measurements can only be performed in the context of the follow-up of patients infected with HIV-1 and/or HIV-2 confirmed by one of the ARL. If the HIV type of the patient is not known in the performing ARL, a copy of the results from another ARL should be provided or the laboratory will first check the infection status of the patient by serology. The ordering physician has to be in charge of the long term follow-up of the patient, preferably in the setting of an HIV Reference Centre (HRC) or in collaboration with an HRC or ARL. 

It is advised to perform viral load measurement

• at the time of diagnosis
• at the time of treatment initiation,
• one month after treatment initiation and
• three months after treatment initiation or until the viral load reaches an undetectable level.

For patients on suppressive antiretroviral therapy between 1 and 4 measurements per year is advisable.

The viral load will be performed with a minimum interval of 3 months between two measurements, except in the following circumstances, to be clearly mentioned on the ordering request:

• At modification of antiretroviral therapy, viral load will be repeated just before (only if the last result is more than one month old), up to one month after and up to 3 months after or until an undetectable viral load is reached.
• After an unexpected increase of the viral load in a patient with stable or undetectable viral load, a new viral load will be performed as soon as possible after checking for compliance problems.
• In pregnant women, the viral load can be performed at shorter intervals, depending on the virological response to treatment.

A viral load measurement should not be performed within 2 to 4 weeks after acute infectious episodes, as for example bacterial pneumonia, Pneumocystis pneumonia or after vaccination, as the viral load can be temporarily increased.

Viral load measurements can be performed in other exceptional circumstances (i.e. HIV-1 RNA detection for early diagnosis). Please contact your ARL for further information.

The lower and upper quantification limits of the currently available tests in Belgium are 20 or 40 copies/ml and 10.000.000 copies/ml for undiluted samples, respectively.

Small variations might occur between different test methods.

To perform a test for viral load measurement in HIV patients:

1. Collect blood in an EDTA-tube by venipuncture (10 ml).
2. Request an HIV viral load. 
3. Store mother-tube at room temperature and send as soon as possible to any clinical laboratory. Plasma should be isolated within one day and stored at -20°C.

Although EDTA plasma is the most appropriate specimen for viral load testing, other specimens such as CSF or serum can be used for some indications. Please contact your ARL for further information.

HIV-2 viral load testing is available but requires dedicated assays. Please contact your ARL for further information.

HIV viral load assays are reported as the number of HIV RNA copies in a milliliter of plasma. If the HIV viral load is detectable, it indicates that HIV is present and replicating. The goal of antiretroviral therapy is to achieve and maintain durable viral suppression that prevents disease progression and limits the risk for onwards transmission.

Please contact an HRC associated specialist in case of:

1. a stable detectable or rising viral load after therapy start,
2. the inability to achieve viral suppression 6 months after therapy start (it might take a few weeks longer to achieve viral suppression when baseline viral load was very high),
3. two independent and consecutive viral loads >50 copies/ml after having achieved a viral load below the quantification limit of your viral load assay.