Someone please help me understand the hep b test?

Question

Someone told me that normally doctors when testing for hep b do a basic antigen test. Which I guess the anitgen is the actual virus. So from that test alone, how would someone know if they were previously infected. Because the basic antigen test that doctors usually use doesn't look for antibodies does it? or do you specifically have to ask for it? Basically I want to know if the normal antigen test that doctors usually perform can tell if someone has had a past infection? I know it can tell if you are currently infected, but what about before? Thanks.

Answer 1

There are 3 antigen tests that indicate current infection and either active or inactive status of the virus.

There is also an antibody test. The B surface antibody test indicates past exposure or previous vaccine, and immunity to Hep B, but cannot distinguish a vaccine from a previous infection. So, if you have received a Hep B vaccine, you would have no way of knowing if you had a Hep B infection in the past (as least that's my understanding - for what its worth).

Better info at this link:

Answer 2

No, you are correct an antigen test will not tell you if you have been previously infected.
The testes they order really depends on what the doctors are trying to find. My lab starts with an antibody test, then moves on to an antigen test if the antibody is positive. So talk to your doctor about it when you go in, explain what you want, and you should be able to get those results. The antibody test is especially important in making decisions about vaccination.

Answer 3

Hepatitis B surface antigen means that the infection is there in the body. IgM antibodies signify a recent infection. IgG antibodies indicate a past infection. When antibodies form, the antigen disappears.