Dr. Remien, first of all thanks for your time you have put into this forum and helping people with their questions. I was wondering how sensetive the Elisa test was? I have heard that sometimes that the Elisa can miss the antibodies in your blood if the count is low is this true? I also was given the Elisa at 10 weeks and it came back negative, I just recently again 13 weeks after my possible exposure to HIV. Can my body produce enough antibodies in just 3 weeks after last test for the elisa to pick up the HIV? And will that 13 week test be a better more reliable test? If the 13 week test does come back negative will it be safe to have sex with my wife again? Thanks for your time it is appreciated!

You are asking a couple of things here. (1) The Elisa test is very sensitive and is more likely to give false "positive" readings than false "negative" readings. That is why it is important to follow up with a Western Blot if there is a positive Elisa. If there is not a positive Elisa, there is no real reason to give a Western Blot. (2) Antibodies can form very quickly in some people, but the general wisdom is that in most cases antibodies are formed within 3 months of infection and that this should be followed up with a test after 6 months. It is very rare for there to be an infection established, without antibodies being formed, after this length of time. If you are unsure about being infected you should use protection with your wife until such time that you know you are not infected.

You may also want to look at the following question and answer on the Safer Sex Forum: http://www.thebody.com/Forums/AIDS/SafeSex/Archive/Testing/Q41734.qna Negative Elisa but Indeterminate WB