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Test to Determine Diagnosis for AIDS

AIDS is diagnosed in HIV-positive people when a capacity of the immune system called cell-mediated immunity is lost; cell-mediated immunity is the immune system's ability to fight off infections on its own. This capacity can be measured as either a pure number of a type of cell (CD4 T-cell) in the blood, or as a percentage of these cells in relationship to other immune cells, known collectively as lymphocytes. AIDS is also diagnosed when an AIDS-defining condition occurs.

  1. CD4 Cell Count

    • CD4 cells are a type of lymphocyte (immune cell) named for a receptor on their surface. These are one of the primary targets of HIV infection, as HIV binds to the CD4 receptor site. As HIV-disease progresses, the CD4 cell count falls, and AIDS is diagnosed when this count falls below 200 per cubic milliliter of blood.

    CD4 Percentage

    • The level of CD4 cells in a person with a healthy immune system varies between individuals and between the sexes, with women tending to have higher overall CD4 cell counts. Because of this variance, some diagnosticians prefer to use a percentage of CD4 cells out of total lymphocytes. When this method is used, a CD4 percentage of 14 per cent or less indicates AIDS, according to the Centers for Disease Control and Prevention (CDC).

    ADIs

    • The appearance of AIDS-defining illnesses (ADIs) is also diagnostic for AIDS. These include four major types of conditions: opportunistic infections, wasting, cancers and neurological problems.

      Opportunistic infections are those that do not cause disease in people with healthy immune systems or cause more severe symptoms in people with compromised immune systems. Some common opportunistic infections include the following: thrush (an oral fungus), cytomegalovirus (which can lead to blindness), toxoplasmosis (a parasitic infection of the brain) and pneumocystis pneumonia.

      Wasting is a condition that causes severe weight loss and is contributed to by both HIV-disease and side effects of antiretroviral drugs used in the treatment of HIV-disease.

      AIDS-defining cancers include Kaposi's sarcoma, a skin cancer caused by opportunistic infection with human herpesvirus-8, and lymphomas, cancers of lymphocytes.

      AIDS dementia complex is an AIDS-defining neurological condition that can affect thinking, motion and behavior.

    Viral Load Testing

    • During the course of HIV-disease, HIV invades and infects other cells, causing them to make copies of HIV instead of participating in the body's immune response. The number of copies of the virus in the system is called the viral load.

      According to the AIDS Education and Training Centers (AIDSETC), viral load testing can be used to monitor the progress of HIV-disease as well as to make decisions about when to begin treatment or to monitor the effectiveness of a course of treatment.

    Treatment

    • The Department of Health and Human Services (DHHS) recommends that treatment for HIV begin when CD4 cell count reaches 350 per cubic milliliter of blood. This occurs before AIDS but after the immune system has become damaged. In countries where testing is difficult to access or unavailable, treatment decisions are made on the basis of the presence of symptoms.

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