What Is the CD4 Count?
A blood test called a CD4 count can determine how many CD4 cells are in the body. A subset of white blood cells is CD4 cells. They are important to the immunological system. They notify other immune cells of the body's infection with bacteria and other viruses. T cells are an immune system subgroup that includes CD4 cells.
What Is a CD4 Lymphocyte Test?
A test called the CD4 count determines how many CD4 cells are present in the blood. T cells, a subset of white blood cells, search the body and eliminate bacteria, viruses, and other foreign microorganisms. The test findings assist the doctor in determining the extent of immune system damage and what is likely to occur next if one does not start antiretroviral therapy (ART).
To assess the success of the treatment and make any required modifications, doctors also monitor CD4 counts. If the ART is working, the CD4 count should increase.
Why Take a Test?
If one has been confirmed to have human immunodeficiency virus (HIV) infection, this test is typically performed to assess the immune system's strength and track the success of treatment; on occasion, it may be used in conjunction with other disorders.
When Will CD4 Lymphocyte Count Be Tested?
When first diagnosed with HIV infection, the immune system should be evaluated as a baseline. After starting antiretroviral therapy (ART), the immune system should be checked every 3 to 6 months to see how well individuals respond.
Why Is CD4 Lymphocyte Test Necessary?
T lymphocytes, also known as T cells, are white blood cells and, a crucial immune system component, are CD4 cells. When combined with an HIV viral load test, CD4 testing assists in determining the quantity of these cells in the blood and the disease state of an individual identified as having human immunodeficiency virus (HIV) infection. The thymus gland produces CD4 lymphocytes, which are transported throughout the body by the blood and lymphatic system. They received their name due to clusters of differentiation (CD) markers on their surfaces. The CD number identifies the precise type of cell. T-helper cells are another name for CD4 cells. They assist in locating, combating, and eliminating particular bacteria, fungi, and viruses that cause diseases. Another important target for HIV is CD4 cells. HIV adheres to the surface of CD4 cells, enters them, and either replicates right away, killing the cells, or it waits and duplicates later. If HIV is left untreated, the viral load rises, the virus replicates inside the cells, and the CD4 cell count eventually decreases. As the illness worsens, the CD4 count declines. If untreated, this process could continue for years until the number of CD4 cells falls to a point where AIDS-related symptoms manifest.
Antiretroviral therapy (ART or ARV), also known as highly active antiretroviral therapy (HAART), is the medication used to treat HIV infection. By lowering the body's HIV (viral load) level, this medication lowers the likelihood of the condition worsening. The CD4 count will rise and stabilize at this point.
Even in healthy persons, CD4 levels might vary. Test findings may alternatively be presented as a CD4 percentage or the proportion of CD4 cells to all lymphocytes to give a clearer picture of the state of the immune system.
Other illnesses, including lymphomas and organ transplants, sometimes call for CD4 testing.
What Does the Test's Outcome Indicate?
Typically, a CD4 count is given as a cell count (expressed as cells per cubic millimeter of blood). Results are occasionally presented as a percentage of all lymphocytes (CD4 percent).
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A typical CD4 count is between 500 and 1,200 cells per cubic millimeter of blood in adults and teenagers. A normal CD4 count generally indicates that HIV infection has not yet significantly impacted the immune system.
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HIV has weakened the immune system, and the disease develops if the CD4 level is low. The immune system can no longer control opportunistic infections at CD4 levels of less than 200 cells per cubic millimeter of blood.
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A medical professional could advise beginning preventative treatment for opportunistic infections like candidiasis (thrush) or Pneumocystis carinii (jiroveci) pneumonia (PCP) at low CD4 counts. Whether or not they exhibit any signs or symptoms, the Centres for Disease Control and Prevention (CDC) classifies individuals with HIV infection, and CD4 counts below 200 cells per cubic millimeter of blood as having AIDS (stage III HIV infection).
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The CD4 levels normally increase and/or stabilize over time once ART has reduced the virus, showing that individuals are responding to treatment. It is typical for the CD4 count to increase by 50–150 cells per cubic millimeter during the first year of treatment.
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However, a gradual change in the CD4 count is often insufficient to alter the course of treatment. The CD4 count rarely decreases, while ART suppresses the virus.
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Even though the health has not changed, it is important to note that anyone CD4 test result could differ from the previous one. Instead of focusing on a single value, a healthcare professional will typically consider a number of CD4 test findings and the trend of CD4 results over time.
Can Illness Other Than HIV Infection Be Diagnosed Using a CD4 Cell Count?
It could be prescribed after an organ transplant to assess how immunosuppressive drugs work. The immune system must be inhibited during transplantation to prevent rejection of the transplanted organ. It is preferable in this situation to have low CD4 cell counts, and a declining count indicates that the medication is effective. Repeating a CD4 count regularly can help assess how well the treatment works.
Sometimes CD4 counts are performed alongside CD8 counts. Another type of lymphocyte called CD8 cells is the cytotoxic T cell or T-suppressor cell. CD8 cells recognize and eliminate virally infected cells.
The CD4 and CD8 cells analysis and the CD4 to CD8 ratio profile may aid lymphoma classification. In addition to CD4 and CD8, other markers on the surface of lymphocytes are typically assessed. The tests assist in distinguishing which specific type of lymphoma is brought on by the growth of B lymphocytes or T lymphocytes. Using this information, doctors can choose the best course of treatment.
Additionally, DiGeorge syndrome, a rare congenital condition characterized, among other things, by low amounts of T lymphocytes in the blood, may be identified using these tests.
Conclusion
The CD4 count does not always accurately represent how an individual with HIV illness feels and performs. For instance, some individuals with higher counts are ill and experience frequent difficulties, whereas others with lower CD4 counts experience few medical issues and perform well. The CD4 count is typically greater in the evening and lower in the morning. The CD4 count may briefly decrease due to acute infections such as pneumonia, influenza, or herpes simplex infection. Chemotherapy for cancer can significantly reduce CD4 count.
