First your doctor tests to see if you have HIV infection. Your blood is tested with an ELISA (enzyme-linked immunosorbent assay) test. If this test is positive for HIV, your blood is tested again with the Western blot test. If both tests are positive, you are diagnosed with HIV infection.

Three things show that a person with HIV infection has gotten AIDS. If any one or more of the following are present, the person has AIDS:

• A CD4 cell count (discussed below) of less than 200

• A CD4 cell percentage of less than 14%

• An AIDS-indicator illness

An AIDS-indicator illness is a physician-diagnosed medical problem that occurs in people with advanced HIV infection. About 25 medical problems are considered AIDS-indicator illnesses. They include conditions like Pneumocystis pneumonia, Kaposi's sarcoma and wasting syndrome. If a person with HIV infection gets an AIDS-indicator illness, that person has AIDS.