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What tests are used to diagnose and monitor HIV?

There are several types of tests associated with HIV disease. Some test for antibodies that the body makes in response to the virus, some test for the concentration of a protein (called p24) found in the virus, some test for the actual number of copies of the virus per millilitre of blood (called viral load testing), some test for levels of immune cells called CD4 cells that are attacked by HIV, and some test for whether patients are resistant to anti-HIV drugs.

  • Antibody testing—to diagnose HIV infection. This test can miss very early HIV infection and should therefore be repeated if there is a high concern about HIV infection.
  • p24 protein testing - may be used to detect early HIV infection. It is now incorporated into most HIV screening tests as a combined antigen/antibody assay.
  • HIV Western Blot - used to confirm HIV infection when an antibody screening test is positive.
  • Multispot HIV-1/HIV-2 test - a rapid enzyme immunoassay used for the detection and differentiation of HIV-1 and HIV-2 antibodies.
  • Viral load testing - determines the amount of virus present in a patient's bloodstream. It is used to decide when to start therapy and to monitor therapy and HIV progression.
  • CD4 T-cell testing—to decide when to start therapy and to monitor therapy, HIV progression, and the status of the immune system.
  • Genotypic resistance testing—to determine if a particular strain of HIV is resistant to the therapy you are on and if the therapy should be switched.

When are these tests requested?

One or more of these tests are ordered after a person is exposed to HIV and decides to be tested, either at the doctor's surgery or a local clinic. Several of the tests listed above are then requested at intervals by a doctor to monitor the course of therapy.

Last Review Date: September 3, 2015