A measurement of the number of CD4 T lymphocytes present in a specific volume of blood, used primarily to assess immune function.
CD4 T cells are immune cells that help coordinate the body’s defense against infections. HIV can infect and progressively reduce these cells, so the CD4 T-cell count is an important measure of how HIV has affected the immune system.
The count is usually reported as cells per microliter (cells/µL) of blood. A lower count generally indicates greater immune suppression, although the result can fluctuate because of infections, medications, time of day, and other factors. In people with HIV, clinicians interpret the CD4 T-cell count together with the viral load, clinical findings, and treatment history.
QUICK FACT
The CD4 T-cell count measures immune cells, not the amount of HIV. The viral load measures the amount of HIV in the blood.
COMMONLY CONFUSED WITH
CD4 T lymphocyte: A CD4 T lymphocyte is an individual type of immune cell; the CD4 T-cell count is the measurement of how many of these cells are present in a given volume of blood.
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