combo test/ first time

Question

HI there,

"The window period for an antigen test is estimated to be from 11 days to one month after exposure to HIV infection.2 It is therefore safest to assume that the test wont cover any potential exposure during the previous month."

http://www.avert.org/testing.htm

"The window period for fourth generation tests is estimated to be about the same as for a p24 antigen test above."

http://www.avert.org/testing.htm

Here's what I don't get.

Some say that 4th generation tests are conclusive at 6 weeks. Does this mean one have to take it the first time within the first month and the second time at 6 weeks?

Regardless of when you think the test is conclusive, do I have to take it the first time during the first month and then a second time at the conclusive point?

my exposure was on 23/jan. when should I take it the first time?

Thanks

Hashem

Answer

Hi Hashem:

Thanks for writing in. You don't HAVE to take a test until 90 days. At 90 days your result will be considered conclusive. You CAN test early if you want the peace of mind. A test at 28 days will give you a good indicator of what your 90 day test result will be. A positive result can be confirmed at any point; a negative result prior to 90 days must be confirmed at the 90 day mark.

The combo antigen/antibody tests work well together because when a person is first infected, the body does not produce enough antibodies that can be detected by a test until around 28 days. However, within the 11-28 day period, the virus produces the p24 antigen in high enough levels that can be detected by the antigen portion of the combo test. The antigen levels slowly fade as the virus establishes itself in the body. As the antigen levels fade, the antigen portion of the combo test becomes less accurate. As the antigen levels are decreasing, the body starts to produce antibodies in response to the virus. These antibodies are what the antibody test looks for.

I hope this helps.

In health,

Richard