The US Food and Drug Administration (FDA) has approved a pioneering rapid HIV test that can simultaneously detect HIV-1 p24 antigen as well as antibodies to both HIV Type 1 and Type 2.

As well as providing faster diagnosis of HIV infection, the new test is also relatively simple to administer in remote 'outreach' settings. These two advantages have huge implications for combating AIDS in sub-Saharan Africa and other underdeveloped areas of the world.

The Alere Determine HIV-1/2 Ag/Ab Combo test is manufactured by Alere's Israel-based Orgenics subsidiary. It can detect HIV antibodies and the HIV-1 p24 antigen in human serum, plasma, and venous or fingerstick whole-blood specimens.

Early tip-off

The HIV-1 p24 antigen test is not definitive but can act as an early 'tip-off' to the presence of HIV-1 infection.

When combined with the presence or absence of HIV-1 and HIV-2 antibodies, the combined test can differentiate an acute onset infection from a more established one.

In acute onset the blood specimen will test positive for HIV-1 p24 antigen but negative for the antibodies. In an established infection, the reverse is usually the case.

The test does not distinguish between antibodies to HIV-1 and HIV-2 so is not useful for screening of blood donors.

Curbing HIV transmission

Dr. Karen Midthun, director of the FDA's Center for Biologics Evaluation and Research, said the new test would enable HIV-infected people to receive medical care sooner thanks to earlier detection in outreach settings.

"Earlier diagnosis may also help to reduce additional HIV transmission," Dr. Midthun added.

HIV infection can lead to AIDS (acquired immune deficiency syndrome), damaging natural defense mechanisms by destroying CD4+ T cells, a type of white blood cell crucial to helping the body fight diseases.

Worldwide, cases of AIDS stem from HIV-1 infection, while HIV-2 infections have mostly been seen in West Africa.

The American Centers for Disease Control and Prevention estimates that each year in the US around 50,000 people are infected with HIV.

It is thought that more than a million people are living with HIV infection in the US, of whom one in five have not yet been diagnosed.