Test Overview

A viral load test measures how much human immunodeficiency virus (HIV) is in the blood. Viral load is first measured when you are diagnosed with HIV infection. This first measurement serves as the baseline. Future viral load measurements will be compared with the baseline. Since viral load can vary from day to day, the trend over time is used to see if the infection is getting worse. If your viral load shows a steady increase over several measurements, it means that the infection is getting worse. If the trend in viral load decreases over several measurements, it means that the infection is being suppressed.

The viral load is measured using one of three different types of tests:

• Reverse-transcriptase polymerase chain reaction (RT-PCR) test
• Branched DNA (bDNA) test
• Nucleic acid sequence-based amplification (NASBA) test

These tests measure the amount of the genetic material (RNA) of HIV in the blood. But each test reports the results in a different way. That's why it's important to use the same test over time.

Why It Is Done

A viral load test is done to watch for changes in an HIV infection. Your doctor uses it to see how well your treatment is working. This information helps guide your treatment options.

A goal of treatment is to reach an undetectable viral load. This result does not mean that you don't have HIV in your blood anymore. It means that the amount of the virus was too low for the test to detect. HIV still can be passed to another person even when the viral load cannot be detected.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Viral load results are reported as the number of HIV copies in a millilitre (copies/mL) of blood. Each virus is called a "copy," because HIV reproduces by making copies of itself (replicating).

If your viral load increases, it means that the infection is getting worse. If the viral load drops, it means that the infection is being suppressed.

An undetectable viral load result doesn't mean that you no longer have HIV in your blood. It simply means that the amount of HIV in the blood was too low for the test to detect. HIV still can be passed to another person even when the viral load cannot be detected.