What is a CD4 count?
A CD4 count is a test that measures the number of CD4 cells in your blood. CD4 cells, also known as T cells, are white blood cells that fight infection and play an important role in your immune system. A CD4 count is used to check the health of the immune system in people infected with HIV (human immunodeficiency virus).
HIV attacks and destroys CD4 cells. If too many CD4 cells are lost, your immune system will have trouble fighting off infections. A CD4 count can help your health care provider find out if you are at risk for serious complications from HIV. The test can also check to see how well HIV medicines are working.
Other names: CD4 lymphocyte count, CD4+ count, T4 count, T-helper cell count, CD4 percent
What is it used for?
A CD4 count may be used to:
- See how HIV is affecting your immune system. This can help your health care provider find out if you are at higher risk for complications from the disease.
- Decide whether to start or change your HIV medicine
- Diagnose AIDS (acquired immunodeficiency syndrome)
- The names HIV and AIDS are both used to describe the same disease. But most people with HIV don’t have AIDS. AIDS is diagnosed when your CD4 count is extremely low.
- AIDS is the most severe form of HIV infection. It badly damages the immune system and can lead to opportunistic infections. These are serious, often life-threatening, conditions that take advantage of very weak immune systems.
You may also need a CD4 count if you’ve had an organ transplant. Organ transplant patients take special medicines to make sure the immune system won’t attack the new organ. For these patients, a low CD4 count is good, and means the medicine is working.
Why do I need a CD4 count?
Your health care provider may order a CD4 count when you are first diagnosed with HIV. You will probably be tested again every few months to see if your counts have changed since your first test. If you are being treated for HIV, your health care provider may order regular CD4 counts to see how well your medicines are working.
Your provider may include other tests with your CD4 count, including:
- A CD4-CD8 ratio. CD8 cells are another type of white blood cell in the immune system. CD8 cells kill cancer cells and other invaders. This test compares the numbers of the two cells to get a better idea of immune system function.
- HIV viral load, a test that measures the amount of HIV in your blood.
What happens during a CD4 count?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a CD4 count.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
CD4 results are given as a number of cells per cubic millimeter of blood. Below is a list of typical results. Your results may vary depending on your health and even the lab used for testing. If you have questions about your results, talk to your health care provider.
- Normal: 500–1,200 cells per cubic millimeter
- Abnormal: 250–500 cells per cubic millimeter. It means you have a weakened immune system and may be infected with HIV.
- Abnormal: 200 or fewer cells per cubic millimeter. It indicates AIDS and a high risk of life-threatening opportunistic infections.
While there is no cure for HIV, there are different medicines you can take to protect your immune system and can prevent you from getting AIDS. Today, people with HIV are living longer, with a better quality of life than ever before. If you are living with HIV, it’s important to see your health care provider regularly.