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HIV and AIDS

In HIV+ Individuals Is It Your White Blood Cell Count That Goes Down

12/02/2002

Question:

If you have HIV, is it your white blood cell count that goes down? Most counts I hear about are in the hundreds, but my cell count on a blood test was 6.8 compared to a range of numbers between like 4.8 and 10. Does this number relate to hundreds? Even in this range, isn`t this number a little low?

Answer:

HIV is a virus that attacks specific cells in the body and through a number ways causes damage to these cells. One of the cells HIV attacks are known as white blood cells called lymphocytes. There are many types of white blood cells called neutrophils, basophils, eosinophils and more. Each of these cells has a specific task in the body. The lymphocytes usually represent about 30% of the white blood cells that travel in the bloodstream. Over half of these lymphocytes have a marker on their surface called CD4. These are your CD4+ lymphocytes. They help organize attacks against germs that might harm us. HIV uses the CD4 marker to enter these cells and eventually leads to their death. Over time, you start out with millions of these CD4+ lymphocytes and then you only have a handful left if HIV is left untreated. The way we measure the cells in your blood works like this: First, we draw your blood and then find out how many white blood cells and lymphocytes you have. Next, we send the blood for special testing to find out how many of the lymphocytes have the CD4+ marker. Then we multiply the total number of lymphocytes by the percentage of CD4+ cells. For example, If your white blood cell count=5,000 x 1,000,000 (in other words you have 5 billion white blood cells); and you have 20% lymphocytes or 1,000 x 1,000,000 (1 billion lymphocytes); and you have 10% CD4+ cells or 100 x 1,000,000 (1 million CD4+ lymphocytes). The way that doctors look at this test is that you have a CD4 count=100. Normally, most people have a CD4 count=450-1,000. When your CD4 count drops to 350 most doctors recommend treatment with HIV medicines. When your CD4 count drops below 200 most recommend prevention treatment for PCP (a kind of pneumonia). When your CD4 count drops below 50 this is when you would be most susceptible to germs and serious infections. So, the higher the CD4 count, the less likely you will get sick from other germs. 

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Response by:

Carl   Fichtenbaum, MD Carl Fichtenbaum, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati