These tests detect HIV within weeks of exposure.
For decades, testing for HIV, or human immunodeficiency virus, was much more rudimentary than it is now. The HIV tests available today have progressed and become more effective, according to hematologist Jeffrey Laurence, MD, of Weill Cornell Medicine in New York City.
The earliest HIV test came into use in April 1985. This simple test, known as the Elisa test, checked for antibodies against HIV in the blood. The immune system creates these antibodies in response to infections like HIV, so the presence of antibodies is a sign of HIV infection. Although groundbreaking at the time, the Elisa test had a high false-positive rate, so follow-up tests were always necessary.
Tests for HIV are far more sensitive today, says Dr. Laurence, who has authored more than 150 scientific papers related to AIDS. These newer combination, or fourth-generation, tests check for both antibodies and antigens—the foreign substances that come from the virus—and can detect an HIV infection around three to four weeks after exposure.
Another type of HIV test looks directly for the genetic material of the HIV virus in the blood, not only for the antibodies and antigens. The nucleic acid test (NAT) can detect HIV infection as early as two to seven days after transmission. However, the NAT is pricey, so this test is often only used for high-risk exposure, such as a health care worker who suspects they may have been exposed.
For a needle-free test, someone can also purchase a home HIV testing kit. These DIY tests use an oral swab that you do in your own home and then mail back to the company for testing. While home testing for HIV is a convenient option, Dr. Laurence still recommends making an appointment with a doctor or clinic. Depending on the test results, the patient can more easily have a conversation about immediate treatment options (if the HIV test results come back positive) or counseling on preventing HIV in the future (if negative).
Looking for more information about HIV testing? Here are the guidelines on who should be tested for HIV.
Dr. Laurence is a hematologist and professor of medicine at Weill Cornell Medicine and NewYork-Presbyterian Hospital. He is the senior scientific consultant for programs at amfAR, The Foundation for AIDS Research.
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HIV testing is very important.
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And the kinds of tests that someone
can do have changed over the years.
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The earliest test we had for
HIV developed in April of 1985.
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It was a very simple test, it's called
the ELISA, and it tests for antibodies.
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Way back when it had a fairly
high false positive rate, so
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you needed to do follow-up testing,
something called a Western Blot.
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And it wasn't anywhere near as
sensitive as the tests we have today
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which are now called
Fourth Generation Testing.
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In Fourth Generation Testing,
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we test not only with much more highly
sensitive ELISAs for the antibody itself,
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but we also test for a piece of the AIDS
virus itself called the antigen.
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The antigen, we test for, is the internal
part of the virus, the core of the virus,
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that's known as P24.
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And by a combination of those two tests,
you can be very, very much certain
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that if those are negative, that you're
not HIV infected, within about 3-4 weeks.
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Now if you have a very high risk exposure
in a certain situation such as a needle
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stick with someone who is known to be
HIV positive, we can actually try to get
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communication much earlier than 3-4 weeks
with the antigen and the antibody test.
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And that is doing something called NAT,
N-A-T for nucleic acid testing.
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Where we actually test for part of
genetic material or the virus itself.
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And that test can be in a positive as
early as two days after an HIV infection.
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We usually say about seven days and
it's pretty reliable.
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Now there are also oral tests.
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There are some people that
are just deathly of needles.
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You can do a home kit test.
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You can actually go into a pharmacy and
buy a home testing kit,
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an oral swab, and swab yourself and
put it into a little packet and
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mail it into the company, and
they'll give you information.
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Now I prefer going to a doctor's office
directly or public health clinic.
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Because of the fact that
when the results come back,
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it will be much better if you're HIV
negative to get counseling about,
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this is wonderful, but let's not go back
to the anxiety you had getting this test.
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Let's work on measures to not
have you need this test again.
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And if you're HIV positive, you
immediately say, you're HIV positive and
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this is what we're gonna do about it.