If you have just been diagnosed with HIV, your health care provider will likely perform several laboratory tests, including a CD4 cell count and an HIV viral load test. These two tests will be done regularly during your HIV care. They tell your provider how well your medications are working at controlling the virus and how your immune system is doing.
In this article, you will learn mostly about viral load, although we will touch on CD4 cell count as well.
What Is an HIV Viral Load Test?
A viral load test measures the amount of virus in a specific quantity of blood. Viral loads can be established for different viruses, such as SARS-CoV-2 (the virus that causes COVID-19) or hepatitis B. The higher the viral load, the greater the amount of virus someone has in their body.
For HIV, the number of viral copies in a milliliter of blood (copies/mL) is the standard measurement. A laboratory counts the number of HIV ribonucleic acid (RNA) particles in a blood sample and reports the number of copies/mL. However, the body constantly turns over these particles. “So whatever we are measuring that day is like a Polaroid picture of the last 24 hours,” explained Francesco R. Simonetti, M.B.Ch.B., Ph.D., an assistant professor of medicine at Johns Hopkins School of Medicine in Baltimore. Trends over time are more important than individual measurements.
HIV exists not only in blood but also elsewhere in the body. While an undetectable HIV viral load means a person cannot pass the virus on to their sexual partner(s), it does not mean that they no longer live with HIV. But having an undetectable viral load means their treatment is working and there is a much better chance of living a long and healthy life.
Why HIV Viral Load Tests Are Necessary
When someone is first diagnosed with HIV, a viral load test establishes how advanced their HIV disease already is. Future viral loads are compared against this first measurement, called the baseline. The baseline viral load also helps determine which HIV medications (called antiretrovirals) might work best, since certain drugs are not recommended for people starting treatment with high viral loads.
Antiretroviral medications keep the virus from replicating (a term describing how the virus gets into a cell and then causes an infection). This reduces the viral load over time. Sometimes the medications a particular person is taking are not—or are no longer—effective because their virus has developed resistance against one or more of the drugs they are taking. “We have to look at things over time, so one measurement of 300 might be extremely harmless, but if it’s the timepoint before a ramp up towards 1,000 or 5,000, it’s a very different interpretation and warning,” said Simonetti. Regular viral load tests show such trends.
When To Have Your HIV Viral Load Tested
U.S. guidelines recommend that someone living with HIV have a viral load test:
When they are first diagnosed (baseline, see above).
When they start HIV treatment (antiretroviral therapy).
Every four to eight weeks after starting antiretroviral therapy until the viral load is undetectable.
When their medications are changed, and every four to eight weeks thereafter until the viral load is undetectable.
At regular intervals (determined by your health care provider) while on stable treatment.
Once someone’s HIV is undetectable, viral load tests can be repeated less frequently. After more than a year of undetectable HIV, such testing may only be necessary twice a year. By contrast, if someone has detectable HIV despite treatment and medication changes, more frequent testing may be required. Their HIV may also be tested for resistance to certain antiretroviral drugs.
HIV Viral Load “Blips”
Sometimes the results of a viral load test are unexpected. Someone may, for example, have undetectable HIV for a while and suddenly show a high viral load. This could indicate that there was a problem with the test, or the person could be experiencing a “blip,” a temporary increase in viral load. When there are unexpected results, the test will usually be repeated.
“A blip sometimes means that the steady state, the average viral load of that person, is very slightly below the limit of detection, but it fluctuates over time,” Simonetti said. “If it’s stable, and we are below 200 copies and they don’t increase over time, [this] shouldn’t be a cause of concern,” he added.
HIV Viral Load Testing During Pregnancy
Testing recommendations are also different for pregnant people who are living with HIV. Since viral load can change during pregnancy, it should be tested more frequently at that time. A viral load test should also be performed close to the time when the person is expected to give birth (their “due date”). If a high viral load is found at that time, additional measures may be taken to prevent the baby from acquiring HIV.
What Do HIV Viral Load Test Results Mean?
On your laboratory report, your viral load may be labeled with one of the terms below. Test results should not be viewed in isolation but should be compared with previous results to see the direction in which your viral load is developing. Different laboratories use tests with different cut-offs, as well, so it is a good idea to stick with the same laboratory for all your tests. This will make it easier to compare trends over time.
Here is some of the terminology you may see on viral load reports:
Undetectable Viral Load
An undetectable HIV viral load means that there is so little virus in your blood that your laboratory cannot count it. Some laboratories will report “below the lower limit of quantification” if there are too few RNA particles to count, or “target not detected” (TND) if they cannot find any RNA particles. However, even TND does not mean that someone is no longer living with HIV. Rather, it means that the treatment is working well and the viral load is very low. That is good news!
The specific limits to determine when laboratory results are undetectable vary with the particular test used. “Usually, I’d say what’s important to [people living with HIV] is that they are below quantification of whatever lab test their clinical center is using,” Simonetti explained.
Detectable Viral Load
When a viral load is detectable, this means that there are enough virus copies in the blood sample for the laboratory to count. In the U.S., when someone has a viral load below 200 copies/mL, they are considered “virally suppressed.” At that level, HIV is well controlled. “If there is a stable viremia [virus level] that is below 200 copies, it is extremely unlikely to result in virological failure and selection for drug resistance,” Simonetti said.
Viral loads that remain consistently above that level may indicate that a person’s antiretroviral drug regimen is not working well at controlling their HIV. Possible causes include the virus having become resistant to one or more of the person’s HIV drugs, interactions between the antiretroviral drugs and other medications, and/or problems with taking medications consistently on schedule.
Non-Suppressible Viremia
In rare cases, a person’s viral load remains above 200 copies/mL even after the possible causes listed above have been addressed. “In cases of true non-suppressible viremia, there is no replication, and that virus is simply released from the reservoir, from infected cells. Changing therapy, adding a fourth drug, doesn’t lead to a reduction,” explained Simonetti.
At this time, non-suppressible viremia is usually found by excluding other causes of a consistently detectable viral load. Researchers are working on finding common defects in the virus in people with non-suppressible viremia in order to develop a test for it.
What Is a “Normal” HIV Viral Load?
There is no normal HIV viral load range that applies to everyone. While viral suppression or an undetectable viral load is the ultimate goal, what undetectable means differs among laboratories. “It’s hard to give a single number that would work for everyone because different labs may have different thresholds to report the viral load negative,” Simonetti explained.
A “negative” viral load only means that the amount of HIV in a blood sample is too low for that particular blood test to measure. It does not mean that the person no longer lives with HIV. If someone diagnosed with HIV stops taking their HIV medications, their viral load will almost always rise again, and their health will be at risk.
Viral Load Numbers and What They Mean
| Name | Copies/mL* | Meaning |
|---|---|---|
| Undetectable | Varies by laboratory | The viral load is too low for a specific laboratory’s standard test to measure. HIV is not cured, but there is so little virus that the person cannot pass HIV on to their sexual partner(s). |
| Virally suppressed |
Up to 200 | Medications are keeping HIV in check, and the virus is unlikely to develop resistance against the drugs a person is taking. The person cannot pass HIV on to their sexual partner(s). |
| Detectable/ virologic failure |
Above 200 and rising over time | Antiretroviral medications are not keeping HIV in check, possibly because the virus has developed resistance to the drugs, there are drug interactions, or the person is not taking their medications consistently. |
| Non-suppressible viremia |
Stable, but above 200 | If drug resistance, drug interactions, and adherence issues have been considered and the viral load does not rise further, this may be non-suppressible viremia. In that case, “there is really nothing a current [antiretroviral] regimen can do,” Simonetti explained. |
| High viral load | Above 100,000 | The virus is quickly replicating and weakening the immune system. HIV disease can then progress rapidly. When someone lives with HIV but is not taking antiretroviral medications, their viral load may rise to more than 1 million copies/mL. |
| Blip | Single rise between two undetectable viral loads | The viral load briefly rises to detectable levels but then drops back down again. Such isolated increases are not considered virologic failures, and no further measures beyond repeat testing are needed. |
HIV Viral Loads and CD4 Cell Counts
CD4 cells are a special kind of immune system cell. Normal CD4 cell counts are between 500 and 1,500 cells/mm3. HIV destroys these cells, and fewer immune-fighting cells means a weaker immune system that may not be able to successfully battle more common viruses and bacteria. A CD4 cell count below 200 cells/mm3 in a person living with HIV is considered AIDS.
When HIV drugs stop the virus from reproducing, the viral load should go down and the CD4 cell count should go up. Unlike viral loads, which often drop quickly, it may take a while for the CD4 count to increase. This is especially true if the CD4 count had dropped very low before antiretroviral treatment was started.
CD4 cell counts and HIV viral loads are standard laboratory blood tests for a person living with HIV. Early during treatment, both of these blood tests will be measured regularly. Once the CD4 count rises above 500 cells/mm3 and the viral load remains undetectable over two years, your health care provider may decide that CD4 monitoring may be stopped.
Takeaways
This article included a lot of information. Here are the most important points to remember about HIV viral load tests:
Viral load is the amount of HIV in a specific quantity of blood, measured by a blood test.
Viral load results are reported as the number of copies/mL of HIV.
What’s important are changes in HIV viral load over time (trends), not a single measurement.
HIV viral load tests help providers track how well drug treatment is working.
The HIV viral load is tested when someone is first diagnosed, when they start treatment, when HIV medications are changed, and then regularly throughout someone’s HIV care.
Pregnant people with HIV should have their viral load tested more often than non-pregnant persons.
The HIV viral load test should be repeated if results are unexpected.
There are two basic categories: detectable and undetectable HIV viral load.
If the viral load is detectable, a person can still be virally suppressed, meaning their treatment is working.
Some people may never become virally suppressed, but their HIV does not continue to reproduce.
Temporary viral “blips” (an unexpected increase in a single HIV viral load test) are also possible.
A high viral load usually means a low CD4 count, and vice versa, indicating how well the drug treatment is working and if a person’s immune system is healthy.