Acquired Immunodeficiency Syndrome (AIDS) (cont.)

To diagnose AIDS, the doctor will need (1) a confirmed, positive test for HIV ("HIV positive" test) and (2) evidence of an AIDS-defining condition or severely depleted CD4 cells.

Testing for HIV is a two-step process involving a screening test and a confirmatory test. The first step is usually a screening test that looks for antibodies against the HIV. Specimens for testing come from blood obtained from a vein or a finger stick, an oral swab, or a urine sample. Results can come back in minutes (rapid tests) or can take several days, depending on the method that is used. If the screening HIV test is positive, the results are confirmed by a special test called a Western blot or indirect immunofluorescence assay test. A Western blot detects antibodies to specific components of the virus. The confirmatory test is necessary because the screening test is less accurate and occasionally will be positive in those who do not have HIV.

Another way to diagnose HIV infection is to do a special test to detect viral particles in the blood. These tests detect RNA, DNA, or viral antigens. However, these tests are more commonly used for guiding treatment rather than for diagnosis.

Merely having HIV does not mean a person has AIDS. AIDS is an advanced stage of HIV infection and requires that the person have evidence of a damaged immune system. That evidence comes from at least one of the following:

• The presence of an AIDS-defining condition
• Measuring the CD4 cells in the body and showing that there are fewer than 200 cells per milliliter of blood
• A laboratory result showing that fewer than 14% of lymphocytes are CD4 cells

It is important to remember that any diagnosis of AIDS requires a confirmed, positive test for HIV.

Table 1: AIDS-defining conditions: Note that a diagnosis of AIDS also requires a confirmed, positive test for HIV.

Pneumonia caused by Pneumocystis jiroveci Recurrent severe bacterial pneumonia Recurrent blood infections caused by Salmonella bacteria Candida infection of the esophagus (swallowing tube) or lungs Cytomegalovirus infections including retinitis or infection of other organs Invasive cervical cancer Kaposi sarcoma Selected types of lymphoma, including Burkitt, immunoblastic, or lymphomas that start in the brain Wasting syndrome caused by HIV Certain parasites in the intestinal tract that cause intractable diarrhea: cryptosporidiosis, isosporiasis Certain fungal infections if found outside of the lungs: coccidioidomycosis, cryptococcosis, histoplasmosis Tuberculosis in the lungs or outside the lungs (disseminated) Herpes simplex infections that cause continuous sores, especially in the lung or esophagus Infections with selected mycobacterium (relatives of the tuberculosis bacterium) outside the lung Brain infection or infection of any internal organ with the parasite toxoplasmosis Encephalopathy (brain infection) due to HIV A viral brain infection called progressive multifocal leukoencephalopathy

Source: MedicineNet.com
http://www.medicinenet.com/acquired_immunodeficiency_syndrome_aids/article.htm