A CD4+ count is a blood test to determine how
immune system is working in people who have been
diagnosed with human immunodeficiency virus (HIV). CD4+ cells are a
type of white blood cell. White blood cells are important in fighting
infections. CD4+ cells are also called T-lymphocytes, T-cells, or T-helper
HIV infects CD4+ cells. The number of CD4+ cells helps
determine whether other infections (opportunistic infections) may occur. The pattern of CD4+ counts over time is more
important than any single CD4+ value because the values can change from day to
day. The CD4+ pattern over time shows the effect of the virus on the immune
system. In people infected with HIV who are not getting treated, CD4+ counts
generally decrease as HIV progresses. A low CD4+ count usually indicates a
weakened immune system and a higher chance of getting opportunistic
Why It Is Done
CD4+ counts are done to:
- Monitor how the HIV infection is affecting your
- Help diagnose
acquired immune deficiency syndrome (AIDS). HIV infection can progress to
AIDS, which cannot be cured.
- Help decide when
antiretroviral therapy (ART). This combination of medicines slows the rate that HIV
multiplies in the body.
- Evaluate your risk for other infections
- Decide when to
start treatment to prevent opportunistic infections, such as medicines to
prevent Pneumocystis pneumonia.
A CD4+ cell count taken at the time you are diagnosed
serves as the baseline against which future CD4+ cell counts will be compared.
Your CD4+ cell count is monitored every 3 to 6 months, depending on your health
status, previous CD4+ cell counts, and whether you are taking
antiretroviral therapy medicines.
How To Prepare
Before you have this test, you may have
the opportunity to meet with a counselor so that you understand what the test
results could mean about your HIV infection.
How It Is Done
The health professional drawing blood
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Apply a gauze pad or cotton ball over the needle site as
the needle is removed.
- Apply pressure to the site and then a