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What
is involved in HIV Testing
An HIV test is a relatively simple procedure, involving a small
sample of blood (about 30mls) being taken and then sent to a
laboratory. There are different types of tests currently used
in different parts of Australia. Some of these tests look for
different things and some will identify an HIV infection sooner
after an exposure to HIV than others.
The following is a guide to the types of tests commonly used.
When you go for an HIV test, ask your doctor to explain the
type of test being used, and what the results mean.
1. HIV Antibody Tests
When someone is infected with HIV, their immune system produces
antibodies to attack the HIV-infected cells. There are tests
that can detect the presence of these antibodies. Most people’s
bodies will produce antibodies within a few weeks after an HIV
infection, however, in some cases the period may be up to three
months. If someone has an HIV antibody test shortly after being
exposed to HIV, they may produce a negative result, as their
body may not yet have produced antibodies. The period between
HIV infection and the point where an HIV antibody test will
give an HIV-positive result is called the ‘window period’.
If you think that you have been exposed to HIV very recently,
you may wish to ask your doctor for a different type of test,
like an ‘antigen’ test, (below):
If your HIV antibody result comes back as positive, a
more sensitive confirmatory test is done (an antigen test).
This is done with the original blood sample so there’s
no need to give a second one. If the second test is positive
it means you have been infected with HIV.
If your HIV antibody test result comes back as negative
it means you still cannot say for certain you do not have HIV.
If your exposure to HIV was recent, you may be in the ‘window
period’, where you could be HIV positive, but not yet producing
HIV antibodies. If you have two negative test results a few
months apart, with no risk activity in between, you can be assured
that you do not have HIV.
2. Antigen Tests
Antigen tests look for the HIV virus itself. This type of test
will identify if someone has become HIV positive sooner after
infection than an antibody test. In areas where the antibody
test is the standard test used, an antigen test may be used
when someone has, or may have had a recent exposure to HIV.
3. Combined Tests
New tests have recently become available that test for both
HIV antibodies and antigens. These tests are not available in
all parts of Australia
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