CD4 (T-cell) counts

This is a blood test, which can tell how many CD4 cells (also called T- cells) you have. A person with a healthy immune system can have between 500 and over a thousand of these important white blood cells per millilitre of blood.

CD4, or T-cells, are important because they help make the immune system work effi ciently to deal with, or get rid of, any unwanted bacteria [1]A microscopic organism composed of a single cell. Many bacteria can cause disease in humans., viruses [2]A small infective organism which is incapable of reproducing outside a host cell. or other harmful organisms. But unlike other viruses, HIV actually invades and destroys the CD4 cells. The immune system cannot function well without these cells. Eventually, if it goes unchecked, HIV will begin to destroy the CD4 cells at a faster rate than the body can produce them. When this begins to happen, the number of CD4 cells drops, and because the immune system cannot do its job, it is slowly overwhelmed.

Interpreting CD4 cell counts

If your CD4 count is 500 or less, you may be advised to consider starting antiviral [3]A medication or substance which is active against one or more viruses. May include anti-HIV drugs, but these are more accurately termed antiretrovirals. treatment. If your CD4 count is 350 or less, treatment is clearly recommended. If your CD4 count is 250 or less, this indicates that serious damage has occurred to your immune system. This places you at risk of serious illnesses related to HIV, called ‘opportunistic infections’. If you have 200 CD4 cells or less, antiretroviral [4]A medication or other substance which is active against retroviruses such as HIV. therapy (to control HIV) is recommended, and you may also need to consider treatments called prophylactic treatments, which can minimise the likelihood of your becoming ill with particular infections. Discuss this with your doctor.