[Question #1078] Understanding the Duo test.

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92 months ago
Dear Dr,
11 weeks ago I had unprotected vaginal intercourse with a Dutch escort lady in Amstdm, an unfortunately stupid mistake on my part.
At the time she assured me she tests regularly and was disease free.(clean)
Since the incident she has told me via email multiple times that she is disease-free. But I feel she has to say she is disease free..anything else would be bad for business.

Testing to date..
Determine rapid POC test at 5 weeks
4th gen Duo lab test at 10 weeks (Quest Diagnostics)
Both tests were negative.

With specific reference to the 4th gen Duo test:
From research I clearly see and understand that the Duo test is considered 99.8% conclusive at 4 weeks.
I also see a lot of postings saying the Duo is considered conclusive at 6 weeks by many experts and some agencies.
What I don't understand is (1) how conclusive is the Duo between 7 weeks and 11 weeks?
(2) Does certainty of the test increase from 7 to 11 weeks or dip down then come back up to 99.9% at 12 weeks?
(3) Does certainty change because P24 might not be as detectable during this period and only the antibody portion has value at that point?
(4) which test result would set your mind most at ease
4 week neg Duo
6 week neg Duo
10 week neg Duo
(5) Do I need to retest at 12/13 weeks or is a 10 week neg duo conclusive?

Due to guilt and loss of rational thinking I am struggling to understand/accept my 10 week result and move on.
Concerned it might change by week 12/13.


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Edward W. Hook M.D.
92 months ago
Welcome to our form. I will try to help.  Searching the Internet for information about how the duo test performs can certainly be confusing. Information seen in the package insert and "official" sources tends to be overly conservative and differ from the data found in carefully conducted scientific trials.   Further, consideration of your likelihood of infection needs to be taken in the context not only of test performance but the nature of your exposure.  In your case even before testing, your chances of infection are very low. First most commercial sex workers do not have HIV. This is true for licensed sex workers in Amsterdam.  Second, following a single unprotected genital sexual exposure your average risk of infection if your partner seen happened to be infected with HIV, your probability of infection would be less than one infection in1000 exposures.  Thus, even before testing, your risk of HIV infection was very very low probably in the neighborhood of one in 100,000.

The Duo test checks for HIV infection by detection of either the HIV virus P 24 antigen or antibodies to the virus. The P 24 antigen represents the presence of virus in the blood even before the body has begun to make antibodies, often as appearing as soon as two weeks after infection.  By testing for both antigen and antibody, DUO tests are positive well before antibody only tests.  The antigen appears in the blood first and, as antibodies increase with time, the bind antigen and the antibody is detected from then on.  Good scientific studies indicate that  virtually all persons who acquire HIV have positive DUO,tests within four weeks of exposure. ,in your case, I would advise you to believe your test results.  You did not get HIV from the exposure you described. You can move on with confidence and there is no need for further testing. EWH
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92 months ago
Dear Dr Hook,

Thank you for your feedback and confirmation 
I understand your point about taking a holistic view of exposure/risk and test results. I have read your reply multiple times and given thought to what you have written.

Could you help me understand just one aspect a little more.
I only had a Duo test at 10 weeks.
Am I correct in understanding that the Duo test is equally conclusive from week 4 to week 12 and that week 4 and week 6 are not "sweet spots"?

With thanks.
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Edward W. Hook M.D.
92 months ago
Correct, at any time beyond four weeks, the DUO test results can be counted on and will not change.  All are equally conclusive,    There certainly is no "sweet spot" at week 4 or 6,  EWH---
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92 months ago

Dr Hook,

Thank you for addressing my questions and concerns.

Please know that you folks offer a most valuable service to those of us on this side of the HIV testing process.

Thanks again.

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Edward W. Hook M.D.
92 months ago
We're pleased you found our Forum helpful.  EWH