HIV antigen / antibody

HIV antibody testing is used to determine whether or not a person is infected with HIV. Early treatment of HIV infection and immune system monitoring can greatly improve long-term health. Also, knowing your HIV status may help you change behaviours so that you and others are not put at risk.

Antibodies to the HIV virus can be detected by a screening test called an ELISA. The ELISA method is very sensitive but requires another test, a Western Blot, to confirm the results because false positives can occur.

Antibody testing for HIV should be requested if you think you may have been exposed to HIV. Testing is recommended if:

• You are sexually active (three or more sexual partners in the last 12 months).
• You received a blood transfusion before 1985, or a sexual partner received a transfusion and later tested positive for HIV. (Since 1985, all blood donated in Australia, the UK and the US is tested for HIV, and infection by transfusion is highly unusual.)
• You are uncertain about your partner's sexual behaviour with others.
• You are a male who has had sex with another male.
• You have used street drugs by injection, especially when sharing needles and/or other equipment.
• You have a sexually transmitted disease (STD).
• You are a health care worker with direct exposure to blood at work.
• You are pregnant. (There are now treatments that can greatly reduce the risk that a pregnant woman who has HIV will give the virus to her baby.)
• You are a woman who wants to make sure you are not infected with HIV before getting pregnant.

In Australia the HIV test is free and anonymous. You can be tested by your doctor, at any clinic dealing with STDs or at special clinics for HIV screening. Your doctor is not informed of the clinic result without your permission. Your doctor or clinic staff will give advice about informing sexual partners if your test is positive. You must have a test if you want to become a blood donor, use your sperm for artificial insemination, have an egg implantation or adopt a child.

A healthy individual has no antibodies to HIV. If you test positive for HIV antibodies on both the ELISA and the Western Blot tests, you are considered to be infected with HIV.

Antibody testing will not detect HIV immediately after exposure, during the window before the development of antibodies. If you are tested too soon, your result may be negative despite the fact that you are infected (false negative). Because of this, repeat testing is important. You should have another HIV antibody test in 3 - 6 months from the time of a possible exposure to the virus.