cd4+ count test

test overview

a cd4+ count is a blood test to see how well the immune system is working in people who have been diagnosed with 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 cells.

hiv infects cd4+ cells. the number of cd4+ cells helps determine whether other infections (opportunistic infections) may occur. if hiv isn't treated, cd4+ counts generally go down as hiv gets worse. in most cases, a low cd4+ count means you have a weakened immune system and a higher chance of getting opportunistic infections.

why it is done

cd4+ counts are done to:

• keep track of how the hiv infection is affecting your immune system.
• help diagnose aids. if you don't get treatment, hiv infection can progress to aids.
• check to see if you're at risk for other infections (opportunistic infections).
• decide whether to start treatment to prevent opportunistic infections, such as medicines to prevent pneumocystis pneumonia.

how often your cd4+ count is checked depends on your treatment, your health, and your prior cd4+ count results.

how to prepare

in general, there's nothing you have to do before this test unless your doctor tells you to.

how it is done

a health professional uses a needle to take a blood sample, usually from the arm.

watch

how it feels

when a blood sample is taken, you may feel nothing at all from the needle. or you might feel a quick sting or pinch.

risks

there is very little chance of having a problem from this test. when a blood sample is taken, a small bruise may form at the site.

results

in people who have hiv, the cd4+ count almost always goes up with treatment. low cd4+ counts make infections more likely.