Definition

T cells are a type of white blood cell crucial to the body’s immune defense. There are four main types of T cells, each with distinct functions:

• CD4 cells are helper cells that initiate the immune response when the body encounters pathogens.

• Suppressor cells help to inhibit or stop the immune response once the infection has been cleared.

• Memory cells remain after the pathogen has been fought off and act as "markers" to recognize the pathogen if it returns.

• CD8 cells are known as killer cells, responsible for destroying infected cells that house viruses, bacteria, or other harmful pathogens.

CD4 and CD8 cells work together in responding to infections, and the balance between these two cell types is an important indicator of HIV infection. The CD8 cells attack pathogens, while CD4 cells trigger the immune response when a pathogen is detected. Once the immune system has cleared the infection, CD8 cells "turn off" the activity of CD4 cells. The CD8 test is commonly conducted alongside the CD4 test to determine the CD4/CD8 ratio, which is important in understanding the progression of HIV infection.

Indication

The CD8 test is primarily used to provide an overview of the extent to which HIV has affected the immune system. This helps doctors assess the damage and potential risk of complications from the disease, particularly in patients who have been newly diagnosed with HIV.

Contraindication

There are no specific contraindications for the CD8 test.

Preparation Before the Test

No special preparation is necessary before the CD8 test. However, you do not need to fast unless you are undergoing additional tests that require fasting. Be sure to inform your doctor about any medications, vitamins, or supplements you are currently taking. It’s also important to remain calm and relaxed during the test. If you are on any medication, discuss with your doctor which medications might need to be paused before the test.

Test Procedure

The CD8 test involves drawing a blood sample, usually from a vein in the arm. The healthcare provider will first apply a band to your upper arm to make the veins more visible. Then, the area where the needle will be inserted will be cleaned with an alcohol swab to prevent infection.

A needle connected to a sample tube will be inserted into your vein to collect a small amount of blood. You may feel a slight sting when the needle goes in. The entire blood sample collection process typically takes just a few minutes.

Normal and Abnormal Values

The normal range for the CD8 test is between 150 to 1000 cells/mm³. Values falling outside this range, either below or above, are considered abnormal.

Results and Recommendations (Follow-up Tests)

Test results can vary based on factors like age, gender, medical history, and other health conditions. Additionally, results may differ depending on the laboratory conducting the test. It is important to discuss your test results with your doctor to understand their significance.

The CD8 test is often conducted alongside the CD4 test, as this allows the CD4/CD8 ratio to be calculated. A high CD8 value may suggest conditions such as HIV/AIDS, spinal issues (particularly related to chemotherapy), anemia, or chronic infections. On the other hand, low CD8 values could indicate serious infections, viral infections, or even potential blood cancers. If your CD8 count is low but increases again, or if it remains normal but then rises, your doctor may reconsider your treatment plan to ensure it is still appropriate.

Consult the Right Doctor

If your CD8 test results are abnormal, it is recommended to consult a general practitioner for an appropriate diagnosis and treatment. If necessary, you may be referred to an internal medicine specialist for a more tailored treatment plan. Your doctor may also suggest additional tests, such as bone density tests, or other diagnostic procedures, to help make a more accurate diagnosis.

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