|What is the significance of %CD4?
Jun 7, 1999
I was infected at the beginning of March 1999. On March 24 my VL was 6.7 million. On April 1, I began Combivir and Viracept; VL 4.5 million, CD4 count 428, %CD4 26. On April 18, VL 3,100 no CD4 count done. On May 27 VL 720, CD4 786, %CD4 28. My doctor said this is a pretty good response to therapy and we should stick to this combo. I would have liked to see a faster drop but what really concerns me is why my %CD4 has changed so little. What is the significance of this number? Thanks
Response from Dr. Cohen
Thanks for the details.
Well... overall the percent is just another way to measure these cells. The small increase in this value at this point is not at all a concern.
When antivirals work - and HIV stops growing - then the CD4 count tends to increase. In your case it has increased dramatically - like 300 cells. We have learned that this initial change may reflect a redistribution of these cells from your lymph nodes to your blood stream - the next months will reflect the actual increase of the number of these cells in the body. There are two common ways to monitor this increase - one is just the number of these cells (the t4 count) in a cubic milliliter of blood - an area smaller than the period at the end of this sentence (altho if your period is the same size an an millimeter, it may be time to buy a newer monitor...). The other way to measure - instead of just counting the number of these cells - is to have a machine count one hundred "T" type immune cells - and then tell us of these hundred cells, how many are helper types (t4) and how many were suppressor types (t8). This helper measurement is your CD4 percent - since the number out of hundred cells is a percent (see you knew you should have been paying attention in fifth grade...). In fact - the percent is what most machines actually do for us - the CD4 count is then calculated after this measure of percent is done, based on how many lymphocytes you have in this drop of blood. Again - the percent is based on counting a hundred T cells; the count is based on how many are in a drop (cubic ml) of blood.
These are related, but different. So usually the count and percent tell us similar things - BUT there is much less variation in the measures of percent than in the measures of CD4 count - since the count is also influenced by how many lymphocytes you have as well in that drop. So the T4 count does bounce around a lot more, while the percent just gradually changes. Successful treatment of HIV usually results in increasing numbers in both measures - and at week 8 your CD4% being just a bit up is expected and not a concern at all.
Oh yeah - your viral load response also sounds reassuring - dropping to nearly 400 by week eight. Just keep monitoring it carefully - given that you were recently infected, and had a very high viral load when you started treatment - many of our standard triples can be somewhat less successful in that case. Be sure to not miss a dose - this is likely especially important in someone with a high viral load. And if your load does not continue to drop steadily in these next weeks - usually to near 50 copies by week 24 or so - you would have the option to consider "intensifying" your combo with a fourth med - since it may require four antivirals for some who start with this high initial viral load.
Hope that clarifies. CC
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