CD4+ Count Test

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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.

Credits

Current as of: September 8, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Peter Shalit MD, PhD - Internal Medicine




The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.