1) am I understanding this correctly? Antigen is actually part of the virus, antibodies are what your body makes to fight off the virus. Once Antibodies are created it's possible that no antigens will be detected?

If that's correct, my question is : let's say you're a normal, healthy person , you get tested at 3 months but for whatever reason your body isn't creating antibodies- at this point would antigens will be detectable?

Also, I've read that 3 months is conclusive unless you have an auto immune disorder, are an IV drug user, on meds for HIV or Hep C. What is actually going on to/in your body that makes the test 6 months and not 3?
Thank you
Hello, and Thank you for contacting AIDSVancouver Helpline. You're asking great questions and I'll be glad to answer them for you.

Antigen is simply parts of any bacteria or virus that enters the body. So yes, in this case the HIV antigens are the physical parts of the actual virus. As you mentioned, antibodies are made by your body to bind the specific antigens in order to fight off the virus. After the HIV virus has entered the body, it will usually take a few weeks for the antibodies to be produced by the body. At that point the HIV tests can detect the antibodies, but they can also detect the HIV antigens since new viruses are constantly produced. So a test such as "4th generation EIA", also called the duo test can be useful to detect both antibodies and antigens, and is considered conclusive after 3 months post-exposure.

However, there are only 4 exceptions where the HIV tests may take longer than 3 months:

1) If you are being treated for Hep C
2) If you have other immunodeficiency disorders
3) if you are on P.E.P (Post-exposure prophylaxis) treatment for HIV
4) If you are having chemotherapy treatment for cancer

The HepC treatment and chemotherapy can suppress the body's ability to produce antibodies, and therefore it can delay the immune response against the HIV virus. In the case of P.E.P treatment (which is taken immediately after exposure to HIV in order to try and eliminate the virus), it can hinder the virus from reproducing quickly, and therefore it will be more difficult to detect the viral antigens, and the antibody response may be delayed. Immune deficiency disorders could cause issues with antibody production, since the immune system is "weaker" and may not respond to the HIV virus very efficiently. However in this case the antigen could still be detected.

I hope I have answered your question. If you like more information please contact us again, or visit You can also take a look at for some good information on HIV testing.

In Health,
Ali, Helpline Volunteer

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