HIV infection is usually screened for with an HIV antibody test or a combination test for HIV antibody and antigen (p24). If the screening test is positive, it must be followed with another test, such as a second antibody test that can differentiate HIV-1 and HIV-2. If results of the first and second test do not agree, then the next test to perform is an HIV-1 RNA test (nucleic acid amplification test, NAAT). If either the second antibody test or the HIV-1 RNA is positive, then the person tested is diagnosed with HIV infection. Read the article on HIV Antibody for more details.
You and your healthcare provider should discuss your treatment options to determine what will work best for you. The Mayo Clinic web page HIV/AIDS: Treatments and drugs has detailed information on various therapies.
4. Is a CD4 cell count used in conditions other than HIV infection?
Yes. It may be ordered when a person has had an organ transplant to help evaluate the effect of immunosuppressive medications. In transplantation, the immune system must be suppressed so that it does not attack the transplanted organ and cause rejection. In this case, it is desirable to have low levels of CD4 cells, and a decreased count shows that the drug is working. A CD4 count may be repeated periodically to monitor the effectiveness of therapy.
CD4 counts are sometimes done in conjunction with CD8 counts. CD8 cells are another type of lymphocyte called T-suppressor cell or cytotoxic T cell. CD8 cells identify and kill cells that have been infected with viruses or that have been affected by cancer.
Evaluation of CD4 and CD8 cells may be used to help classify lymphomas. Typically, several markers on the surface of lymphocytes in addition to CD4 and CD8 are evaluated. The tests help determine whether the lymphoma is due to the proliferation of B lymphocytes or T lymphocytes and which specific type. This information is useful in determining appropriate therapy.
These tests may also help diagnose DiGeorge syndrome, a rare congenital disorder characterized by, among other things, low levels of T cells in the blood. For more information on DiGeorge syndrome, visit the Mayo Clinic web site.
5. My report includes a CD4/CD8 ratio. What is it?
It is the number of CD4 cells compared to the number of CD8 cells. In HIV infections, CD4 cells are usually destroyed more rapidly than CD8 cells. Because absolute CD4 counts can vary from day to day, it is sometimes useful to look at the CD4 count compared to the CD8 count to get a clear picture of the health of the immune system. In general, the CD4/CD8 ratio decreases as HIV infection progresses, and the ratio should increase and/or stabilize when treatment is effective.
This article was last reviewed on July 23, 2015. | This article was last modified on October 1, 2015.
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