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Avatar universal

HIV Duo Test - 28 Day Test?

Firstly may I say what a help this forum has been to me since a recent sexual exposure and I hope everyone continues the good work at Med Help!

My question is related to the reliability of the HIV duo test at 28 days?

I had unprotected oral sex with an African sex worker in Germany five weeks ago. There is a possibility we had sex, but due to being heavily drunk I honestly cannot remember.
She spoke fluent German so I presume she has resided there for some time.

I did go back the next morning and she said we did not have sex, but also denied oral sex without a condom so this it what leaves me to believe there is a degree of dishonesty in what she told me. She told me she was married and had three children so why should she want to put herself at risk?

Anyway I went for standard STD test after one week at a GUM clinic and all results came back two weeks later negative. At 28 days I went for HIV Duo test and results came back negative. I have had no symptoms of any kind.

The Doctor at the clinic said it was safe for me to have sex again with my wife and I could be 99.9% certain that I did not have any STD / HIV. Only test I was told to take again at 3 months was syphillis.

Apologies for the detail here, but from reading the forum it appears the more information helps the doctor to answer questions reliabily.

The questions I have are:

1. I was told the risk of this encounter is les than 1%, (would you agree).

2. I was told the chances of the test being wrong are less than 1% and in three years and well over 5,000 tests, since starting using this test they had never had a wrong diagnosis, is this a relaible test in your opinion?

3. Doctor told me more than 99% of HIV cases can be diagnosed after 28 days by detecting P24 antigen which is alwys present pre HIV and the GUM clinics are behind the times in making people wait for 3 months, do you agree with this statement?

4.I was told only reason to take the test again at 3 months would be for peace of mind, but it will be negative, so I should get on with my life, is this a fair assumption?

5. If there is a 1% chance this test is wrong, surely sleeping with my wife is ethically incorrect, until I test again at 3 months?

6. After blood test I developed a bruise 4 inches long and 2 inches wide on my arm, it is not sore in the slightest and the doctor said it will simply be either a burst capilary or not enogh pressure applied after blood was taken, I am convinced this is HIV related, am I being stupid?

The anxiety I have been feeling over the past five weeks is killing me, I cannot sleep / cannot eat without feeling sick and the guilt I am feeling is overwhelming - I feel like I have given both myself and my wife a death sentance.

Appreciate your response...

28 Responses
239123 tn?1267647614
You have had accurate advice by the GUM clinic; they know as much as I do about the test and its reliability.  

1) Definitely less than 1%, if you had sex (which apparently you didn't), and even if your partner had HIV.  2, 3) Those estimates are reasonable.  4) I agree.  5) I disagree; you can have sex with your wife any time you wish.*  6) There is no chance that symptom is due to HIV.

*Assume a 10% chance your partner had HIV, and that you had unprotected sex.  If she was infected, the chance you got HIV during a single episode of vaginal sex was around 1 in 2000.  Also assume the test has a 1% chance of missing HIV.  Your odds of having HIV despite the negative test are 0.1 x 0.0005 x 0.01 = 0.0000005.  That's 1 in 2 million.  Anyway, your partner says you didn't have sex, so the true risk probably is zero.

Your problem is your guilt over your infidelity.  Get counseling if you cannot get over your irrational fear of HIV, which simply is not an issue.

Please no "yes but" or "what if" questions.  I will have no further responses.

Avatar universal
Thanks for the prompt response Dr. HHH you have helped ease my worries and I suppose like a lot of other users of the forum I just wanted an answer to my specific circumstances from a second source, i.e. a second opinion.

Only comment I would like to add is to other users of the forum I have a test scheduled at WEEK 8 which I will post the results to on this thread, (although I know it will be negative) for reference purposes.


Avatar universal
doc, are you saying that a duo test (4th gen elisa) at 28 days is really close to 99%?  I'm not doubting you, Im just wondering.  Is there a time in which the p24 becomes undetectable as well as the antibodies or is there an overlap?

also, does the .0005 = 1/2000 or is it .005
Avatar universal
Hi there I was told its actually more like 99.8% reliable and given supporting documentation to prove this, (in releation to a false negative test).



I phoned my doctor back this morning and he explained that the reason people will state the 99% figure, (or even less i.e. 98%) is due to a number of assays that have been writtten showing false positives, false negatives are even rarer. As many people come back despite his advice for three month test he AGAIN clarified to me that he had never had a false negative after thousands of tests at the 90 day stage.

Other factor to consider is high risk situation, i.e. needle sharing or anal sex with a confirmed HIV+ partern. Even if there was penetrative vaginal sex, my case was still categorised as "Low Risk".

I was also told that one of his biggest problems regarding HIV is peoples lack of ability to believe what the doctors tell them, i.e. if your doctor confirmed you where negative for a suspected cancerous lump would you question this synopsis? He also asked me in todays modern era of patients suing for smaller errors, do you honestly think the medical profession would risk giving out false advice. By the way my doctor has been specialising in mens health for seven years.

The most important lesson I have been told to take from this experience is to practice safe sex where STD / HIV status is not known and move on with my life instead of wasting hours searching on the internet for doomsday news, I woke up this morning with a completely different outlook on this experience.

Hope this information helps?

For the doctor no "if" or "but" questions but more to keep consistancy throughout the forum you state 1 in 2000 as the figure for transmission risk for one unprotected sexual act, but everyhwere else on this site the figure is stated as 1 in 1000? Also I did not understand the relevance of the 0.0005 figure? (sorry to question your answer)
Avatar universal
in all due respect the artiles which you have posted do indeed claim a 99.8 rate but don't specify as to when or at what day.  I know you would really like to forget this as would I, I just had a 4 week duo test as well, but I would wait until the 7-8 week mark to be safe.. thats just me though.
Avatar universal
Understanding I have is that the P24 Antigen would be picked up before HIV antibodies 99.8% of the time and as the test also looks at both strands of HIV in the event that you had developed antibody then this would be picked up anyway - I am led to believe there is no overlap period, but during my paranoid phase I did not find any articles discussing this - my Doctor said only important point was that the test was taken after 3 weeks / 21 days, to be safe that is why they insist on 28 days.

Anyway even if the test was lets say only 90% accurate, (which I am convinced is not the case, the chances of 1) the person being infected, 2) you actually obtaining HIV and 3) the test producing false negative is still in the tens of thousands.

Have you had STD tests, as this brings the odds down even more in your favour, look at the rates of STD among a population of people, (which are a lot higher than HIV) then the chances of catching one, (which are hundreds of times grater than HIV) and think to yourself I am clean of STD and in a great number of HIV cases other STD is present.

I think to put your mind at rest you should use the statistical model that Dr. HHH illustrates earlier in this thread and try and apply it to your situation - I have been told this by two seperate doctors living in different continents with different medical experiences, so for me this is good enough.

Only reason I am going back for the test at eight weeks is due to my local GUM clinic wanting to build up a database on all people tested.

GOOD LUCK, maybe you can complete this thread concerning HIV DUO test with your results so others have a reference?

Avatar universal
I will follow up on my thread for future refrence on this site:  6/21 "Oh great, condom breaks and shes on her period"  for refrence for this site.  NO STDs and a 4 week neg on 4th gen elisa.  The question of a delay between post p24 recognition and elisa antibody recognition is one question I have not been able to find.  Im hoping that there is no time in which the test becomes undetectable between the two tests.
Avatar universal
Have a look at this site, states P24 protein will become undetected after HIV antibodies have been produced, but more importantly states at this point the standard HIV antibody test will be positive...


Hope this helps?
150689 tn?1333990045
Hi, I had a very similar experience recently. The Doctor who performed my DUO test (28 days after expsoure) was also of the same opinion that the duo test was 99.8% accurate. He also stated that it would have been accurate from 21 days. For the record i went private for the HIV test, but had the STI tests done on the NHS, which also came back as negative.

Obviously it seems this test isn't freely available, if at all on the NHS due to constraints on resources, cost and the number of people who woulld want one. In fact the Doctor who took my test, who had worked in the NHS said it was "dangerously" behind the times when it came to sexual health.

I think in essence the three "3 month rule" is more of a CYA thing than a truly defined window period.

Just to be sure I had a rapid OraSure test done @ 87 days post exposure, which also came back as negative.

In regards to the window period, i just cant see where the 90 days window period works? If it's three months, then thats 12 weeks or 84 days?
Avatar universal
I wonder if US and UK labs use the same tests
Avatar universal
What about an OraQuik II at 17 days?
Avatar universal
? Window period: The time delay from infection to positive EIA
averages 14 to 22 days with newer test reagents. Some do not seroconvert
for 3 to 4 weeks, but virtually all patients seroconvert within 6
months (Am J Med 2000;109:568).

Johns Hopkina University School of Medicine

Avatar universal
Thank you for the information. It was negative and I think I am hust really freakin myself out.  The person who ran the test said I should be good.  I am going to test again this weekend.  I was able to talk to the person I was with and she said she was fine.  Just really scared.  I have a head cold that is not helping.
Avatar universal
Early Detection and the Window Period
Specific antibody to HIV is produced shortly after infection, but the exact time depends on several factors, including host and viral characteristics. Importantly, antibody may be present at low levels during early infection but not at the detection limit of some assays. Using the early generation tests, antibody could be detected in most individuals by 6 to 12 weeks after infection. Newer generation assays, including the third-generation antigen sandwich assays, can detect antibody at about 3 to 4 weeks after infection.(2) As discussed in other chapters, this window period before the detection of antibody can be shortened by several days using antigen tests, and by several more days using nucleic acid detection methods.(3) Therefore, in most individuals, the window period may only be 2 to 3 weeks if an all-inclusive testing strategy is used. Most antibody tests currently on the market have near perfect and equivalent degrees of sensitivity for detecting most individuals who are infected with HIV (epidemiologic sensitivity), but they vary in their ability to detect low levels of antibody (analytical sensitivity), such as that occurring before complete seroconversion.(2) Although tests are available to detect specific HIV IgM antibody, these tests have shown little utility in identifying early infection because IgM responses to HIV are not consistently produced during early infection.(4) The ability of some tests (e.g., third-generation tests) to detect IgM antibody simultaneously with IgG detection, however, may be responsible for their higher analytical sensitivity.
Avatar universal
Just out of interest where did you get your test performed? I used Freedom Health in London...

NHS will not even test me in UK now until after 3 months, which is why I am definately going back, hopefully they will change there policy over the next few years so peopele who cannot afford a private health clinic do not have to wait for 3 months to test
150689 tn?1333990045
Lol! Same here. And would use them again and recommend them to anyone who would need to be tested for HIV or other STI's.
Avatar universal
Hi guys, I was wondering if you knew whether the p24 antigen test combined with an antibody test is widely done in the States.  You mentioned this Freedomhealth clinic in  the UK.  Would it be easy to find clinics that also do this Duo test in the States? Any recommendations, suggestions would be very helpful. I was just thinking of  contacting a major hospital near where I live on the East Coast. I worry about an exposure that took place 3 weeks ago, hence I'd like to go for the Duo.
Avatar universal
Just wondering whether you had unprotected vaginal sex in your case, while at the doctors today for a routine check-up he advised me that only @ the three months stage should I start sleeping with my wife again - which unfortuanely has started my anxiety all over again !!
150689 tn?1333990045
No. I was assualted. It's been a f*****g horrible time the past few months. But I've tested and tested again; 28 and 87 days - 1 month and 3 months.

I totally know where you're coming from with the anxitey though. I still have days when it's not so good. But I'm starting to let go. Two neg tests out to the 3 month mark are pretty conclusive.

Can't keep trying to convince yourself your poz though! Every do i've spoken to has told me that i should accept i'm neg.

IN fact when i went back to FH they told me that further testing wasn't warranted, but thety if i needed peace of mind.
150689 tn?1333990045
Gotta say though I didn't have unprotected sex with my wife until i had the 3 month test done.

Probably not what you want to hear. But you have my support mate. Sure it's all good!
239123 tn?1267647614
Your new thread was an inappropriate one; the discussion could and should have been continued here.  A limited number of new threads can be accommodated each day, so unnecessary ones block others with new questions. I deleted it.

I have been asked and answered the same question many times before:  No, I have never seen a patient with negative HIV test 4 weeks after exposure who later turned up positive.

I'm not going to get into comments on whether or not particular clinics are following proper procedures.

This is my last comment in this thread.

Avatar universal
I meant to add that I fully understand why your clinic got upset with you returning to re-ask the same questions!  Perhaps you can tell I am having the identical reaction.

Avatar universal
Just wanted to give you an update to my scenario just returned from GUM clinic after 7 week test - negative HIV 1+2 and negative P24 test. I am told that I can consider myself 99% + in the clear, in fact when asked if it was OK to have unprotected sex with my wife Dr. said I see no reason why not - he said "even with one encounter of unprotected sex with possible infected sex worker, (originating from Cameroon) I had now tested more than enough and rather than worry about the less than 1%, (IF MY PARTNER WAS INFECTED) I need to move on with my life". As a closing comment, (which I found amusing) "Please no calls if you sneeze / cough / get the runs after a curry / sweat after a night on the tiles / find a new spot on your penis that has been there since you were born / etc"

Not sure if anyone else has felt the same anxiety I have over the last few weeks, (trust me at times suicidal) but it has all but gone away - I just hope the feeling lasts?


10 days all STD negative
30 days negative for HIV 1 + HIV 2 + P24 Antigen
49 days negative for HIV 1 + HIV 2 + P24 Antigen

Good Karma to all the worried wells out there !!

P.S. Will I re-test @ 12 weeks, (who knows but if I do I will be sure to let you all know - for now I will live happilly with my less than 1% chance of infection)
Avatar universal
Me and my husband had a 3 some with other woman and the condom bust wild he was having sex with the next person  my husband went for a Hiv test it came back negative and 40 day after me and the next woman went for our HIV test all 3 person HIV test came back negative  .Do u think i should still worry about being infected? .

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