Hep B antigen test

[skier2413]

I tested negative for a Hep B antigen test 9 weeks after possible though unlikely exposure. I was wondering what the waiting period for a conclusive test is. Thank you.

[Edward W Hook, MD]

You should have been tested for both hepatitis B antigen and antibody.  Most infections are  apparent after two months. You can have complete confidence in the result after three months.  If this is something you worry about and you do not have hepatitis B antibodies, you should get the vaccine.  EWH

[skier2413]

I did not get tested for antibodies because I am part way through the vaccination process. Six or seven years ago I had the first test in the series. I intend to take the rest of the series. Does the first part of the vaccination grant any protection? Also I read at the CDC that antigen tests will become positive between 1-9 months after exposure, so is the 2 to 3 month positive test development fairly rare?

[Edward W Hook, MD]

The initial vaccination will provide partial protection.  Just how much is difficult to say, particularly given the long time since your inital vaccination..  

Most persons who get HBV will have positive tests within a few months.  In your partially vaccinated state, it might take a little longer if you were to become infected but not much.  The 6-9 month figure is quite conservative and designed to pick up "stragglers".  EWH

[skier2413]

Sorry I meant to say nine weeks. CDC says 1-9 weeks will develop a positive surface antigen test. That seems liberal compared to other things I have heard so I am confused. I know the other antigen test can take longer. Sorry about not being more specific.

[Edward W Hook, MD]

And I apologze as well.  I was talking about the antibody test.  Let's start again.

ANTIGEN tests for hepatits B..  Should develop in less than 2 months for sure and nearly all before 6 weeks.

Antibodies - there are a series of antibodies, the first to develop is to the "core" antigen, the second to the surface antigen.  Core antibody develops before surface antibody and is the better indicator of infection as both infection and the vaccine can induce antibodies to the surface antigen.  HBcAB  (the core antibody) has typically developed within 2-6 (rarely out to 8) weeks.

Finally, it is not helpful to compare development of antibodies to one virus such as hepatitis B to the time for development of antibodies to another (like HIV).  They are different orgqanisms which induce different types of antibody responses.  I hope we have things staight now.  EWH

[skier2413]

Thank you for the clarification I feel quite relieved. This has been a frustrating situation for me because the state of Washington epidimologist provides data for the antigen test which states a surface antigen test can take six months to become positive. The averages they give for time for a positive test to occur mirror the average times for symptoms to occur. It is as if they have their information mixed up some how. I am going to go with your advice and the cdc's because they make more sense (labcorp says their surface antigen test can detect well before acutal symptoms). It might almost be good for a professional to politely ask them to reevaluate their data as they are giving out completely different information that may cause people months of anxiety. Thank your very much again for your time.