WHAT DO THE NUMBERS MEAN?

WHAT DO THE NUMBERS MEAN?

The meaning of CD8 cell counts is not clear, but it is being studied.

The CD4 cell count is a key measure of the health of the immune system. The lower the count, the greater damage HIV has done. Anyone who has less than 200 CD4 cells, or a CD4 percentage less than 14%, is considered to have AIDS according to the US Centers for Disease Control.

CD4 counts are used together with the viral load to estimate how long someone will stay healthy. See Fact Sheet 125 for more information on the viral load test.

CD4 counts are also used to indicate when to start certain types of drug therapy:
When to start antiretroviral therapy (ART):

When the CD4 count goes below 350, most health care providers begin ART (see Fact Sheet 403). Also, some health care providers use the CD4% going below 15% as a sign to start aggressive ART, even if the CD4 count is high. More conservative health care providers might wait until the CD4 count drops to near 200 before starting treatment. A recent study found that starting treatment with a CD4% below 5% was strongly linked to a poor outcome.
When to start drugs to prevent opportunistic infections:

Most health care providers prescribe drugs to prevent opportunistic infections at the following CD4 levels:

* Less than 200: pneumocystis pneumonia (PCP)
* Less than 100: toxoplasmosis and cryptococcosis
* Less than 75: mycobacterium avium complex (MAC).

Because they are such an important indicator of the strength of the immune system, official treatment guideline in the US suggest that CD4 counts be monitored every 3 to 4 months. See Fact Sheet 404 for more information on the treatment guidelines.