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
How It Feels
You may feel nothing at all from the
needle puncture, or you may feel a brief sting or pinch as the needle goes
through the skin. Some people feel a stinging pain while the needle is in the
vein. But many people do not feel any pain (or have only minor discomfort) after
the needle is positioned in the vein. The amount of pain you feel depends on
the skill of the health professional drawing the blood, the condition of your
veins, and your sensitivity to pain.