|%CD4 - What does this mean?
Apr 2, 2008
My viral load is 6,000 copies/ml and my CD4 is 594. Based on the above, I have some time to go before I start my meds.
However, my %CD4 is 20%. It was 19% 3 months ago. What does this mean? I am told that the a normal reading is 26-40%. Is there a cause for concern? Thank you.
| Response from Dr. Frascino
I see it's time for a review of what CD4 cells are and how we monitor them in HIV infection. So beginning with the basics, a CD4 cell is a type of lymphocyte, which in turn is a type of white blood cell. CD4 cells (also called T-cells) are an integral part of the body's immune system. HIV specifically infect CD4 T-cells by actually becoming part of the cell and using the cell's machinery to make lots of new copies of HIV, which then go out and infect more CD4 cells. Clever, eh? However, the HIV-infected CD4 cells eventually die, which is not so clever, because as HIV wipes out CD4 cells, the immune system is weakened and the HIVer eventually becomes sick and dies. There are millions of different types of CD4 cells and each one is specifically designed to fight a specific type of invading germ. As these cells get wiped out, we lose the ability to fight certain infections and become more likely to acquire "opportunistic infections" that wouldn't normally affect or bother someone with a normal immune system (normal CD4 count). You can think of opportunistic infections as taking advantage of an "opportunity." The opportunity provided by our depressed or deficient immune system allows these germs to do us harm.
The absolute CD4 cell count bounces around significantly, as it is influenced by a number of factors, including time of day, stress/fatigue levels, non-HIV concurrent infections, etc. Infections have the largest impact on CD4 cell counts. Whenever your body fights any infection, the number of white blood cells goes up and consequently the number of CD4 cells rises as well. Vaccinations can also cause this same effect. That's why it's best not to check your CD4 cell count until you've completely recovered from an infection.
Absolute CD4 cell counts are reported per cubic milliliter of blood. (The normal range varies somewhat from lab to lab, but is usually around 500 to 1,600. Because CD4 counts are so variable, we often prefer to monitor CD4 percentage, the percentage of total lymphocytes comprised by CD4 cells. For example, if your CD4% is 20%, one out of five lymphocytes is a CD4 cell. This percentage is more stable than the absolute number of CD4 cells, as it is less affected by the factors mentioned above. The normal range is usually 20% to 40%. A CD4% below 14% indicates severe immune deficiency and is a criterion for the AIDS diagnosis, as is an absolute CD4 count below 200.
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Be well. Stay well.
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