Difference between CD4 and Percentage (CD4 count versus CD4%, 2011) (LACK OF CD4 RESPONSE DESPITE TREATMENT, 2011)

Question

Could someone explain what exactly is the correlation between CD4 cells and percentage. I know what CD4 are but what does percentage mean. Also, I have been undetectable for 1 year now, my percentage has gone from 3 to 8 but cd4 rose to 320 from 130 but after reaching the 320 mark, it keeps dropping at every 3 months check up. My recent labs were done last week and once again cd4 dropped another 30 points and its down to 190. It is so frustrating. I would think, having been undetectable for a year and continue to be, my cd4 cells should have kept climbing like the percentage keeps climbing. I am very discouraged and don't know what to think. Clearly, my hiv doctor has not been able to explain what does all that mean. Please help explain. Thanks a million.

Answer

Hi.

This gets a bit confusing, but let me try to sort this out for you. A CD4 count is not a direct cell count of CD4 cells in your blood. Rather, it's a calculation based on the total white blood cell count and the proportion of those white cells that are CD4 cells. Consequently the absolute CD4 cell count is not exact, but rather a calculated estimate. CD4 cell counts can and do vary quite a bit due to many different factors -- diurnal variation, coinfection, etc. Because of this variability many HIV specialist physicians, including yours truly, also closely monitor CD4 percentage. CD4 percentage is the percentage of your lymphocytes (a subcategory of white blood cells) that are CD4 cells. So if your CD4% is 30%, 30% of your lymphocytes are CD4 cells. CD4% is much more stable than absolute CD4 cell counts. See link below.

You should be encouraged your CD4% continues to climb and that your HIV plasma viral load remains undetectable. This indicates your current antiretroviral regimen is effective both virologically (driving your HIV viral load to undetectable levels) and immunologically (increasing CD4%). There are a number of potential reasons for lack of a robust CD4/CD4% response to antiretroviral therapy. See link below.

Good luck.

Dr. Bob

CD4 fell from 525 to 265 in 8 months (CD4 count versus CD4%, 2011) Jul 13, 2011

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