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 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 cells.

HIV infects CD4+ cells. The number of CD4+ cells helps determine whether other infections (opportunistic infections) may occur. In people infected with HIV who are not getting treated, CD4+ counts generally decrease as HIV progresses. A low CD4+ count usually means a weakened immune system and a higher chance of getting opportunistic infections.

Why It Is Done

CD4+ counts are done to:

• Monitor how the HIV infection is affecting your immune system.
• Help diagnose acquired immune deficiency syndrome (AIDS). If you don't get treatment, HIV infection can progress to AIDS.
• Evaluate your risk for other infections (opportunistic infections).
• Decide when 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

Before you have this test, you may have the opportunity to meet with a counsellor so that you understand what the test results could mean about your HIV infection.

How It Is Done

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

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 with HIV, the CD4+ count almost always goes up with treatment. Low CD4+ counts make infections more likely.