Blood work:
Two common tests to use for
monitoring HIV disease

January 2008     View PDF     En español

CD4 cell count tests

Your doctor normally will order tests of several types of white blood cells (WBCs). One is a B cell, which is involved in the production of antibodies. B cells also deal with infections that are outside cells. Another type of WBC is a CD8+ cell, which deals with infections that are inside cells. The third type is a CD4 cell, which “helps” B cells and CD8+ cells do their jobs. All three of these WBCs are also called lymphocytes.

In HIV-negative people, normal CD4 cell counts are 600–1,500/mm3 of blood. Normal CD8+ cell counts are 300–800/mm3. In general, people have 2-to-1 ratios of CD4 to CD8+ cells. So for every two CD4 cells, an HIV-negative person has one CD8+ cell in their blood.

However, in most people living with HIV, the virus normally causes a slow decline in their CD4 cells over time. And, among those who are not on anti-HIV therapy, it’s common for the normal CD4/CD8+ ratio to be reversed.

Besides looking at these cell counts, it’s also helpful to look at the relative percentages of CD4 and CD8+ cells in a blood sample. The CD4 percentage is the percentage of CD4 cells in the total lymphocyte count. The normal range is 28–58%.