Falling CD4 count with stable CD4 %
Nov 27, 2006
First up, a big thank you to you for giving your expertise and time to answer questions like mine. I wish we had a forum like this in the UK.
I have been HIV positive since Jan 2006. All of my CD4 counts until recently have been 820-860. My CD% started and has remained at 22%. However, at my last blood my CD4 had dropped to 680 (21%). My questions are:
1. I understand that my CD4 % represents the proportion of my total white blood cells that are CD4 cells. So if CD4 changes but the percentage remains the same, am I right in thinking this represents a shift of all WBCs in or out of my bloodstream rather than a drop in CD4 in blood due to HIV activity?
2. If the answer to 1 is "yes" then what is the importance of CD4 % beyond showing whether a change in CD4 is due to HIV or not? I have read that a CD4 % <20% carries the same risk for developing AIDS as having a CD4 of 200! This doesn't make sense to me.
3. Although my CD4 has dropped this time, causing me concern, so has my viral load (to 98,000 now from >500,000 initially via 158,000 and 256,000). I have read research showing that viral load is responsible for about 5% of the decrease in CD4 count. What are other likely mechanisms causing CD4 depletion independent of absolute viral load?
Response from Dr. Wohl
You are on the right track. The CD4% is the proportion of white blood cells (WBC) that are CD4. So, if the CD4% is the same, a modest drop in the absolute CD4 cell count is probably meaningless (as in your case).
The CD4% is very meaningful if it is low as the smaller the propotion of WBCs that are CD4, the worse off one is. A CD4% of 7%, let's say, demonstrates that very feww WBC are CD4 cells whether the absolute CD4 count is 50 or 150.
I am unclear about the source of the relationship between viral load and CD4 decline you mention. The rate of CD4 cell drop is indeed related to the viral load, the higher the viral load, the quicker the CD4 cells decline. The major cause of CD4 decline is HIV. Some drugs can do it as can malnutrition.
As an aside, your viral load suggests that you may have been recently infected and that your virus is reaching its set point - the level it will generally stay at.
Hope that helps.
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