What is a 'CD4 count'?

What is a 'CD4 count'?

Charles Farthing (Chief of Medicine, AIDS Healthcare Foundation) gives expert video advice on: Why do I need to take lab tests if I have HIV? and more...

The CD4 count is a count of the number of CD4 cells in the blood. It's usually expressed per cubic millimetre of blood, but it's really the same as per CC. The CD4 cell is a specialised type of lymphocyte which is a specialized type of white cell in the blood that is the one that gets infected by HIV sometimes called the T-cell or T-helper cell. It's all referring to same thing. So, the CD4 count in a normal individual is between something like 500 and 1500 per cubic millimetre of blood. In someone who has HIV infection, it's often reduced, and we use the cut-off for HIV as 200. If it's below 200 per cubic millimetre of blood, we say the patient has Aids.