Does this test have other names?
CD4/CD8 ratio T-cell test
What is this test?
This test looks at the ratio of two important types of white blood cells in your blood.
Lymphocytes are a type of white blood cell in your immune system. This test looks
at two of them, CD4 and CD8. CD4 cells lead the fight against infections. CD8 cells
can kill cancer cells and other invaders.
If you have HIV, your CD4 cell count may be low. Without HIV treatment, your number
of CD4 cells will likely keep falling. A lack of CD4 cells usually leads to more frequent
This test looks at the ratio of CD4 cells to CD8 cells. The ratio tells your healthcare
provider how strong your immune system is and helps predict how likely you are to
develop a crippling infection.
In addition to HIV/AIDS, conditions that can be monitored with this test include infectious
mononucleosis and other viral infections, chronic lymphocytic leukemia, Hodgkin disease,
aplastic anemia, and neurological disorders like multiple sclerosis and myasthenia
Why do I need this test?
You may need this test if your healthcare provider thinks you have HIV. Some people
infected with HIV may develop flu-like symptoms within a few weeks of getting the
virus. But other people have no symptoms at all.
Although the test looks at the ratio of CD4 cells to CD8 cells, your healthcare provider
may focus on the results of the CD4 count.
You may also have this test to see how well HIV treatment is working.
What other tests might I have along with this test?
Your healthcare provider may also order other tests to help diagnose HIV. These include:
Complete blood count
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Results for the ratio are given as a number. The results for each cell count are given
as a number per cubic millimeter (/mm3).
A normal CD4/CD8 ratio is 2.0, with CD4 lymphocytes equal to or greater than 400/mm3 and CD8 lymphocytes equal to 200 to 800/mm3.
If your ratio is higher than 2, it means your immune system is strong and you may
not have HIV.
If your ratio is less than 1, you may have:
AIDS if your CD4 count is less than 200/mm3
Bone marrow problems related to chemotherapy
Multiple sclerosis, myasthenia gravis, or another nervous system condition
Higher than normal results may mean you have:
Type of blood cancer
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Pregnancy can affect your results. Women with HIV may have higher levels of white
blood cells, which affects the proportion of CD4 cells. Drinking too much alcohol
can also affect your results. Certain medicines such as corticosteroids can affect
How do I get ready for this test?
You don't need to prepare for this test. But tell your healthcare provider if you
are pregnant, are a heavy alcohol user, or are taking medicines that could affect
your white blood cell count. In addition, be sure your provider knows about all medicines,
herbs, vitamins, and supplements you are taking. This includes medicines that don't
need a prescription and any illicit drugs you may use.