Question

Why do we use CD4% as well as CD4 counts?

30 March 2010. Related: All topics, CD4 and viral load.

I was recently diagnosed HIV positive and had my first set of results back last week. My CD4% was 32% and this, I was told, was good. My CD4 was 330 and viral load was 9000. My doctor explained how my CD4 might have been low this time round as it was taken on the day I got confirmation of my status and I was very stressed.

My question relates to CD4%. I was told by my doctor that around 30% was normal. Can you explain what a low CD4% value would be? At what value of CD4% would starting treatment be recommended? What is the normal progression of CD4% values?

Answer

Answer: Charlotte Walker

Thank you for your question.

Finding out you are HIV positive is not easy. As well as dealing with the emotional stress, there is a lot of new information to learn and take on board. It is great that you are actively trying to find the answers to your questions.

CD4 fluctuations are common. CD4 count results can depend on many things such as the time of day a test is done, exercise, menstrual cycle, stress, how much sleep you had, other underlying infections, vaccinations and lab mistakes

Only a small proportion of CD4 cells are found in the blood, the rest are found in either your lymph nodes or tissues. The CD4 cells travel between the blood, the lymph nodes and tissues. This movement of CD4 cells in and out of the blood could also cause a lower one-off test result.

Your CD4% tends to be more stable than the absolute CD4 count. Therefore doctors rely more on the CD4% than they do CD4 count. It takes into account factors, which can cause a false high or false low CD4 count. CD4% measures the amount of CD4 cells in the blood compared to the overall number of white blood cells in the blood. It gives an overall picture of your immune system.

A HIV negative person has a CD4% or approximately 40% although everyone varies depending on their individual immune system. A CD4% of 29% is about the same as a count of over 500 cells/mm3 but there is a wider range for higher values.

Your CD4% of 32 is therefore very good. A CD4% between 12-15% is equivalent to under 200 cells/mm3.

The progression of CD4% values is similar to that of the CD4 count. As the HIV infection progresses and the viral load increases, the CD4 count and CD4% will decrease until it is time to begin HIV medication.

For further information please see a similar question here or follow this link to a simple explanation of the differences between CD4 count and CD4%.