POZ IRELAND
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POZ IRELAND
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C D4 (T Cell) COUNTSCD4 Cell: Also known as "T4" or "helper T cell," the CD4 cell is the primary target of HIV. It performs critical functions such as signalling other parts of the immune system to respond to an infection. Treatment decisions are often based on Viral Load and CD4 count. Normal counts range from 500 to 1500. CD4 counts in uninfected adults A normal CD4 count in a man without HIV infection will be approximately 400 to 1200 cells per cubic millimetre of blood, and 500 to 1600 in women. CD4 count in HIV infectionCD4 count is a marker of likely disease progression. Initially in HIV infection there is a sharp drop in the CD4 count and then the count levels off to around 500-600 cells. The best CD4 count to give an accurate prediction for the future is the most recent count. Irregular counts (those unexpectedly high and low) may be laboratory errors or real temporary or sustained changes which should be checked by repeating the count. CD4 counts can also be used to predict the risks for particular conditions such as Pneumocystis carinii pneumonia, CMV disease or MAI disease. This can help decide who will benefit from prophylactic (preventative) therapy. For instance PCP prophylaxis is strongly recommended after the CD4 count has fallen below 200, and MAI prophylaxis is being recommended more often when the CD4 count is below 75-100.
CD4 percentage The proportion of all lymphocytes that are CD4 cells is called the CD4 percentage. In HIV-negative people, a normal result is 40%. Among HIV-positive people the CD4 percentage tends to decline as HIV disease progresses. Some doctors argue that this is potentially the most accurate CD4 test, although it is not very sensitive to small changes. It can be particularly useful if you receive a CD4 result that you are not expecting, for example a sudden drop. If the immune system is being damaged by HIV, then one could expect the percentage of all lymphocytes to have decreased. However, if the percentage stays the same it is more likely that you had an infection which your immune system was dealing with, which caused your CD4 count to drop. Definitions: CD4/CD8 Ratio: This number is a reflection of the health of the immune system. The normal ratio is between 1 and 4. In HIV infection the CD4 count is often decreased and the CD8 count increased so the ratio might ‘invert’, that is become less than 1. CD8 Cell: A subtype of T lymphocytes that has traditionally been seen as a "suppressor" cell, one that shuts off the immune system when an invading organism is eliminated. CD8 cells also perform active immunity functions, such as killing certain infected cells. CD4 Count - Every 3-6 months. Repeat for decisions on antiretroviral therapy and prophylaxis of opportunistic infections, or when counts do not make sense. Routine tests when counts are <50/mm3 are of little use only if monitoring response to antiretroviral therapy.
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