Dr. MJ Bazos MD,
HIV and Plasma Viral
What is a plasma viral load
A plasma viral load test (also called a PVL
test) measures how much HIV is in your blood. The amount of HIV in your blood is
called your viral load. HIV means "human immunodeficiency virus."
If your doctor knows your viral load, he or she
can tell more about your risk of health problems caused by HIV infection. A PVL
test helps your doctor decide if it is time for you to start taking medicines
for HIV or to change to different medicines.
Three different PVL tests can be used:
- The polymerase chain reaction (PCR) test
- The branched-chain DNA (bDNA) test
- The nucleic acid sequence-based amplification
All of these tests
work well. Each of them can give a slightly different number for the amount of
HIV in your blood. It is good to use the same test each time.
Changes in PVL are often called log changes. A
log change means 10 times more or 10 times less than a previous PVL test result.
For example, if your PVL test shows that you used to have 20,000 HIV copies per
mL of plasma, a log change would be either an increase to 200,000 copies per mL
or a decrease to 2,000 copies per mL.
The amount of HIV in your blood may change. That
is why decisions about your HIV medicines are usually made after your doctor has
checked 2 PVL tests done 2 to 3 weeks apart.
How does a PVL test help my doctor
decide when to start HIV medicines?
If you have not started taking medicines for HIV
infection, your doctor will usually want to test your PVL several times a year
to see if the amount of HIV in your blood is changing.
Your doctor might think about starting you on
HIV medicines if your PVL is higher than 10,000 to 30,000 copies per mL. This is
a complicated decision to make. Your doctor has to think about the other
medicines you are taking and the other health problems you have. A PVL test
result may lead to different decisions for every person.
Another measurement that can be taken with the
PVL test is the CD4+ cell count. The CD4+ cell count helps to show how healthy
your immune system is. When the PVL test score goes down, the CD4+ cell count
usually goes up, although this might take some time. CD4+ cell counts can also
help you and your doctor decide when to start or change HIV medicines. Your
doctor will talk with you about the decision to start HIV medicines.
How are PVL tests used during HIV
If you are already taking medicines to treat HIV
infection, your doctor will want you to get a PVL test several times a year to
make sure that the medicines keep working for you. If your PVL goes up, you and
your doctor will have to talk about changing your HIV medicines.
Your doctor might also want you to have a PVL
test if you get another infection or if your CD4+ cell count goes down.
It is usually best not to get a PVL test for 3
to 4 weeks after you have an immunization (a "shot") or for 1 month after you
have an infection. Your PVL could be higher than usual at these times.
What do HIV medicines do to the PVL?
After you start taking HIV medicines or change
to different medicines, your PVL should go down at least 1 log (10 times) in the
first 1 to 2 months. Your PVL should keep going down after that. If the
medicines are working for you, after 4 to 6 months your PVL will get so low that
it will be almost impossible to detect. An undetectable level is good, but it
does not mean that you are cured or that HIV is completely out of your body. Not
everyone's PVL gets this low.
How fast your PVL goes down depends on many
things including the following:
- How high it was to begin with
- How carefully you are taking your medicines
- Whether you were taking other HIV medicines
Special tests show
that even people with undetectable levels of HIV still have very small amounts
of the virus in their blood. So even if your HIV level is undetectable, you need
to get PVL tests several times a year. You could still infect other people if
you have unsafe sex (sex without a condom) or if you share a needle.
Why is a low PVL good?
There is no cure for HIV infection, but keeping
a low PVL level helps you feel well.