T-cell Test Definitions, from AIDSmeds.com

 


CD3+ Absolute Count

The CD3+ count represents the total number of T Lymphocytes, a type of white blood cell that matures in the Thymus Gland. These include the T4 & T8 cells.

 

 

 


CD3 Percentage

The total T Lymphocyte Count (including T4 & T8 cells) as a percentage of Total Lymphocytes, which are white blood cells that mature and reside in the lymphoid organs of the body.

 

 


T4 Cell Count

The number of T4 cells per cubic millimeter of blood (a drop, more or less). These cells are white blood cells that turn the immune system on to fight disease, and are also the primary target of HIV. As HIV disease progresses, the T4 cells fall from a normal count of 500-1500 down to as low as zero. When the T-cell count goes below 200, there is an increased risk of opportunistic infections, and when the T-cell count drops below 50, the risk rises dramatically.

 


T4 Percentage

The T4 Count as a percentage of Total Lymphocytes, which are white blood cells that mature and reside in the lymphoid organs of the body. The T4 percentage is sometimes a more reliable measurement than the T4 count because it tends to vary less between measurements.

 

 


T8 Cell Count

The number of T8 cells per cubic millimeter of blood (a drop, more or less). Even though most test results refer to these as Suppressor cells, the count actually includes both Suppressor and Killer T-cells (see definitions above). The T8 cell count is usually elevated in people infected by HIV, but since little is known as to why this is, the test result is rarely used in making treatment decisions.

 


T8 Percentage

The T8 Count as a percentage of Total Lymphocytes, which are white blood cells that mature and reside in the lymphoid organs of the body. The T8 percentage is sometimes a more reliable measurement than the T8 count because it tends to vary less between measurements.

 

 


The T-Cell Ratio

The T4 Count divided by the T8 Count. Since the T4 count is usually lower than normal in people living with HIV, and the T8 count is usually higher, the ratio is usually much lower than normal. A normal ratio is usually between 0.9 and 6.0. Like the T8 cell count, nobody really knows what this low number means. However, most experts agree that once anti-HIV therapy is started, an increase in the T-cell ratio (i.e. a rising T4 count and a falling T8 count) is a tell-tale sign that drug treatment is working.

 

 

 

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