CD4 Test
The CD4 test measures the number of CD4 cells (a type of white blood cell) in the blood. These cells help fight infections and are a key indicator of immune system strength. In people living with HIV, the virus attacks and destroys CD4 cells. A lower CD4 count means a weaker immune system and a higher risk of infections. Doctors use the CD4 test to monitor the health of HIV-positive individuals and to decide when to start or adjust antiretroviral therapy (ART).