WHAT FACTORS INFLUENCE A CD4 CELL COUNT?

WHAT FACTORS INFLUENCE A CD4 CELL COUNT?

The CD4 cell value bounces around a lot. Time of day, fatigue, and stress can affect the test results. It’s best to have blood drawn at the same time of day for each CD4 cell test, and to use the same laboratory.

Infections can have a large impact on CD4 cell counts. When your body fights an infection, the number of white blood cells (lymphocytes) goes up. CD4 and CD8 counts go up, too. Vaccinations can cause the same effects. Don’t check your CD4 cells until a couple of weeks after you recover from an infection or get a vaccination.
HOW ARE THE TEST RESULTS REPORTED?

CD4 cell tests are normally reported as the number of cells in a cubic millimeter of blood, or mm3. There is some disagreement about the normal range for CD4 cell counts, but normal CD4 counts are between 500 and 1600, and CD8 counts are between 375 and 1100. CD4 counts drop dramatically in people with HIV, in some cases down to zero.

The ratio of CD4 cells to CD8 cells is often reported. This is calculated by dividing the CD4 value by the CD8 value. In healthy people, this ratio is between 0.9 and 1.9, meaning that there are about 1 to 2 CD4 cells for every CD8 cell. In people with HIV infection, this ratio drops dramatically, meaning that there are many times more CD8 cells than CD4 cells.

Because the CD4 counts are so variable, some health care providers prefer to look at the CD4 percentages. These percentages refer to total lymphocytes. If your test reports CD4% = 34%, that means that 34% of your lymphocytes were CD4 cells. This percentage is more stable than the number of CD4 cells. The normal range is between 20% and 40%. A CD4 percentage below 14% indicates serious immune damage. It is a sign of AIDS in people with HIV infection. A recent study showed that the CD4% is a predictor of HIV disease progression.