Clarification on test for peace of mind

[rolands]

Dr Hunter

Thanks for your time on this forum (both doctors) as it certainly gives alot of information. Alot of the questions seem to be a repeat and with mine may be the same as many before but I wanted to ask based on my situation.
I had used a condom with a CSW which broke during virginal sex and I only noticed after the event. I called to local STD clinic the day after which told me that HIV testing needs six weeks for conclusive testing (Australia). Having read alot on your forum I had a 4th gen combo done at 25day (average time). It was negative. I called the clinic and they said it wasn't conclusive so I waited for six weeks and had another 4th gen combo test. It was negative too.
The doctor said that it was conclusive and that was it. My questions is 1) People on this forum have asked this same question but I couldn't find a 4th gen combo test at six weeks. Is it conclusive? as you mention 6 to 8 weeks or is that figure based on other tests and not a 4th Gen combo.?
2) Have you had or heard of a six week negative 4th Gen combo test being false.?
3) Statistically what would the odds for me to be HIV positive.?
4) Would you recommend a retest.?
5) Is this result/s conclusive and is this the best test to have(4th Gen combo)?
6) Can both antigen/antibody go past 6wks for the test to miss it.

Thank you as I wanted to start the year knowing where I stood.

Roland

[wannaknow81]

A related discussion, Had a Hiv testing at the 14 week,Antibody testing was started.

[Edward W Hook, MD]

This will be the last response.

An ELISA is a test format. There are several different "generations" of ELISA tests for HIV, the most recent being the 4th generation tests.  ELISA tests test for antibodies, sometimes abbreviated as ab. The combo tests also test for HIV peptides (pieces of protein).   All of this however is IRRELEVANT to you as you have no reason for concern at this time.  You need to believe your tests.  You did not get HIV from the exposure you described.  You really need to move on.  My answers however seem to just fuel your anxieties.  Therefore, there will be no further answers.  EWH

[rolands]

Hi Dr Edward

Whats the difference between a ELISA test and a 4th Gen ag/ab combo or is it the same. Thanks

[rolands]

Thank you. I really appreciate your comments and honesty. Happy New Year

[Edward W Hook, MD]

Bottom line, at this time the chances of your having a positive HIV test at this time are far lower than your chances of having a false positive test.  Your tests are to be believed.  I cannot comment on information that is made on the International Forum.  While Dr. Handsfield and I work closely together and are in regular communication we do not work with International HIV group.  They are a well thought of group and, as you can see since you seem to be reading at both sites,  we use different terms and figures.  The data I quote come from reading the medical literature, attending scientific conferences and my own practice in the field for over 30 years and are as accurate as I can be confident in. Finally, as I said, my answers take into account not only the issue of test performance but also the circumstances of your exposure that you mentioned in your original post.  I am confident that there is no meaningful difference between my assessment as "very, very low"  and the assessment as "almost 100%" that you somehow seem to take more comfort in when you read it on the other site.  

Please let me clarify an important point.  As a generalization for both you and other readers, you must realize that we VERY frequently get questions asking if different types of exposures or prevention measures are 100% effective.  The answer to that is that this is scientifically impossible.  For a variety of complex mathematical reasons far too complex to go into here, all one can do with well conducted scientific studies is estimate probabilities.  By definition, any estimate, cannot be 100% certain.  On the other hand, when Dr. Handsfield or I say that something is very close to no risk or of minimal risk, or use any other term to indicate a very small risk, that means "close to zero" in a world where zero cannot be attained.  


My advice is for you to put this bvehind you.  You are not going to find out "in a couple of years" that you got HIV from the exposure you describe.  EWH

[rolands]

Thanks for your feedback. I wanted to clarify a few comments that you made please.
You mentioned in the begining that your colleagues discussed 3rd Gen testing at 8weeks and you said Yes to my first question which was: People on this forum have asked this same question but I couldn't find a 4th gen combo test at six weeks. Is it conclusive? Can I assume you mean that my test is conclusive at six weeks?. On the international forum the doctors mention 99.86% at 25days accuracy and almost 100% at six weeks for one person. Why would this be different to me (you mentioned 95%) at six weeks . The No to retest(4) is confusing as you say Very,Very low or Most in your description to detection and finally what would cause Antigen and or antibody to go past six weeks if some forum threads say near 100% conclusive at 6 weeks. The reasons for the clarity is that I want to put this behind me and I am find some of the responses to be grey and I hope that I am not being rude as I don't want to find out in a couple of years that I have HIV. Botton line have had a person in my situation come back with a postive result after a negative with a 4th gen combo or do you feel in your professional opinion that it can happen. Many thanks

[Edward W Hook, MD]

Welcome to the Forum.  Since the 3rd generation HIV antibody tests have become available neither of us, nor colleagues whom we have discussed the issue with have seen or heard of anyone who had a negative HIV antibody test at 8 weeks who then went on to develop antibodies as a result of HIV infection. The only exception to this are people who have taken anti-HIV medications in failed attempts to prevent infection following a known exposure such as a needle stick.   In theory, someone who was taking intensive chemotherapy for cancer might also experience delayed antibody development as well but I am not aware of such cases since the 3rd generation tests became available.  The antigen detection test which is also present to in the combo tests such as you refer to ad to the speed with which tests would be expected to be positive.  At 6 weeks over 95% of persons exposure to HIV will have developed antibodies and it is reasonable to assume that most of the rest of infections acquired 6 weeks earlier would be detected by the antigen detection test.  Thus, your risk for HIV related to the exposure you report is very, very low.  This is not only because your test is negative but the additional fact that it is unlikely that your partner had HIV and even if she did, HIV is only transmitted about once for every 1000 vaginal sexual exposures.  

To summarize what I have said in answer to your specific questions:
1.  Yes
2.  No.
3.  Somewhere between 1 in a million and 1 in 10 million
4.  No
5.  See above
6. Very, very rarely

EWH