What laboratory tests are used to monitor HIV-infected people?

What laboratory tests are used to monitor HIV-infected people?

Two blood tests are routinely used to monitor HIV-infected people. One of these tests, which counts the number of CD4 cells, assesses the status of the immune system. The other test, which determines the so-called viral load, directly measures the amount of virus in the blood.

In individuals not infected with HIV, the CD4 count in the blood is normally above 400 cells per cubic milliliter (mm³) of blood. HIV-infected people generally do not become at risk for complications until their CD4 cells are fewer than 200 cells per mm³. At this level of CD4 cells, the immune system does not function adequately and is considered suppressed. A declining number of CD4 cells means that HIV disease is advancing. Thus, a low CD4 cell count signals that the person is at risk for one of the many unusual infections (the so-called opportunistic infections) that occur in individuals who are immunosuppressed. In addition, the actual CD4 cell count indicates which specific therapies should be initiated to prevent those infections.