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The HIV antibody test
   Last updated: 18.06.04
 
The test for HIV is called an HIV antibody test. Antibodies are the body's response to an infection. Antibodies normally begin to appear in your blood a few weeks after you become infected with HIV.

The HIV antibody test detects the presence of antibodies to HIV in the blood or saliva. It is easier and cheaper to detect antibodies to HIV than it is to look for the virus itself.

Even if you're found to be HIV antibody positive, this doesn't predict which HIV–related conditions may or may not develop. All it tells you is whether there are HIV antibodies in your blood. It is not a test for AIDS.

HIV (or Human Immunodeficiency Virus) is the virus that can cause AIDS. But not everyone with HIV infection has developed AIDS. In fact, we know that after being infected for ten years, about one in three people still don't have any symptoms of AIDS.

However, without treatment, two–thirds of adults infected with HIV are likely to develop AIDS within ten years of being exposed to HIV. In countries where people are exposed to tuberculosis and parasitic diseases such as malaria, this period is likely to be shorter. It is also shorter for children born with the virus.

The window period
HIV antibodies don't appear the day after you become infected, so it is not possible to find out if you have been infected immediately after a possible risk. Antibodies usually take between one and two months to appear in your blood. The time between infection and the development of antibodies is called the window period.

In the window period people infected with HIV have no antibodies in their blood, but may already have very high levels of HIV in their blood, sexual fluids or breast milk. In fact, people with HIV are most infectious during this window period before their own immune system has tried to control the virus. So you could pass on HIV to another person during this period even though an antibody test shows that you are HIV-negative.

Clinics generally recommend that you wait three months from the time of a possible risk before taking an antibody test, to be sure that a negative result is truly negative. However, if you have been at unusual risk or have reason to believe you may have been infected, you should not delay in seeking advice.