Antigen/antibody combo HIV test

Originally Published: August 20, 2010
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Dear Alice,

I read about the new test approved by the FDA for HIV 1 and 2. When will it be available?

Dear Reader,

The mighty magic eight ball says: Cannot predict now. On June 21, 2010, the U.S. Food and Drug Administration (FDA) released a statement announcing the approval of a new HIV test that may aid in the diagnosis of recent HIV infections. Unfortunately, when this test will be available to the general public isn't clear. According to the FDA press release, it isn't intended to be used for routine screenings but will instead be used in clinical and public health laboratories, as well as in cases where the more widely used tests are impractical or unavailable, such as urgent blood transfusions.

This test, ARCHITECT HIV Ag/Ab Combo Assay, is able to simultaneously test for the HIV antigen (Ag) and HIV antibody (Ab). A brief biology lesson:

Antigens are molecules located on the outside of bacteria and viruses, like HIV, that the immune system recognizes as being "foreign" and need to be attacked.
Antibodies are proteins that the immune system uses to identify and neutralize "foreign" objects, like viruses. When the immune system detects a foreign antigen, it creates an antibody to "match" the antigen. Each antibody binds specifically to an antigen, like a lock with its key. Antibodies float around in the blood or other bodily fluids.

Most HIV tests are HIV antibody tests because antibodies are more abundant, flow in several bodily fluids, and are larger and easier to detect. HIV antigen tests are less common because antigens are harder to find (they're on the tiny viruses) and harder to detect. Testing for HIV antigen has a particular advantage: early detection.

When a person becomes infected with HIV, it usually takes the immune system two to twelve weeks to manufacture the antibody, a.k.a. the three month "window period" for HIV antibody tests. Newly infected people pose a great concern in HIV prevention to others if they remain undetected because of the window period of HIV antibody tests. By detecting the antigen on the virus itself, HIV antigen tests close this gap considerably, though not completely, to about one to two weeks. The ARCHITECT HIV test can simultaneously test for both the HIV antigen and antibody, making it a double threat to detect HIV infection.

Like several other HIV tests, this test is able to detect both HIV 1 and 2. HIV 1 is the most common form throughout the world whereas HIV 2 is present primarily in West Africa, though cases of HIV 2 have sprung up elsewhere. This HIV test may aid HIV diagnosis in adults including pregnant women. This is the first assay test approved for use among children as young as two years old.

Your fate with this test may seem unclear, but if you are interested in getting tested, most city and state health departments offer a variety of HIV tests for free. Tests are almost always either confidential or even anonymous. All Columbia students can get tested by making an appointment on Open Communicator or by calling x4-2284. Counseling and testing services are also available to all Columbia students through the Gay Health Advocacy Project (GHAP). You may not get to try out the ARCHITECT HIV test just yet, but the many available HIV tests can give you the answers you really want to know!

Take care,