127 days ago I had a possible exposure. It was portected vaginal sex, receiving unprotected fellatio and performing unprotected cunnilingus on a 39 year old black woman of African origin. She has been living in Ireland for over a decade. 

Since the exposure I have been tested a number of times. Latest tests are as follows (all negative) 

INSTI test (rapid 3rd gen) - Negative at 111 days. 

Fingerprick 4th Gen - Negative at 121 days. (Collect blood sample from finger, approx 15 drops ina  vial and mail it to the lab. They claim window period of 7 weeks)

Venous sample 4th Gen - Negative at 99 days. 

I know I should draw one very obvious conclusion from these results, but since Saturday (123 days post exposure) I have developed a rash on my stomach and upper arms. It is non itchy, stings at times and not overly painful, although I can feel its presence. It is not hot to touch. 

1) Could a rash appearing 4 months after exposure be linked to that HIV exposure?

2) Have the above tests proved beyond all doubt that I did not acquire HIV from the above exposure? 

3) Can I resume unprotected sex with my regular partner without worry? 

4) What is the window period for the INSTI test and 4th gen test? 

5) I have noted that several sites say that fingerprick 4th gen tests even carried out in the lab may take longer to become positive than venous samples? Is this true and what is the window period for this test? The NHS recently raised theirs from 4 weeks to 7 weeks. 

6) When does a 3rd gen and a 4th gen test rule out HIV-2 infection, as the person was of African origin? 

I have tested negative for other STIs also. 

Thank you. 

The bottom line is that you should not be at all worried. You definitely do not have HIV!

One of the most common themes on this forum is that the HIV blood tests are among the most accurate and reliable diagnostic tests ever developed, for any medical condition. When done sufficiently long after the last possible exposure (4-8 weeks, depending on the specific tests or combinations of tests), negative results overrule all other considerations. No matter how high the risk of HIV at the time of exposure, and no matter what symptoms are present, negative results always are to be trusted. I'll also point out that you had a low risk exposure; and that the kind of skin rash you describe it not at all typical of HIV. However, I am going to suggest you have a blood test for syphilis -- more about which below.

Those comments indirectly answer most of your questions, but to be explicit:

1) Your negative test results prove HIV is not the cause of the rash.

2) Yes, your multiple negative tests are absolutely conclusive.

3) If I had been in your situation, I probably would never have stopped having unprotected sex with my wife. Certainly you could have safely resumed sex at home long before now.

4) All third generation tests, including INSTI, 8 weeks -- although some experts recommend 12 weeks to be extra certain. All antigen-antibody (4th generation) tests -- almost always 4 weeks, but rarely as long as 6 weeks -- never more than that.

5) Fingerstick tests are exceedingly accurate and take no longer to become positive than lab-based tests. (Many agencies used to say 4 weeks but changed their advice to 6 weeks about 3 years ago. The actual figure in an important published scientific review said 45 days, a bit beyond 6 weeks but not quite 7 weeks -- which may explains why NHS cites 7 weeks. In any case, you had at least a couple of tests well beyond that time limit. 

6) HIV2 is virtually absent in North American and Western European countries, except in recent immigrants from endemic areas and their regular sex partners. In any case, the antibody tests are 100% reliable in detecting HIV 2 by 8-12 weeks.

Going back to my syphilis comment:  I'm glad your other STI tests were negative, but you don't state the timing of whatever syphilis test(s) you had. If you had a syphilis blood test at least 6 weeks after the exposure, you can be confident in that result. However, the timing of the rash and the fact that it isn't very irritating ("hot to the touch") is consistent with secondary syphilis. Probably it's something else, but if any doubt at all about what test was done and the timing, it can't hurt to have another syphilis blood test at this time. Better safe than sorry.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

My latest syphilis tests were as follows:

Venous sample igg/igm test at 99 days post exposure. 

Fingerprick sample EIA test at 119 days post exposure. 

Both negative. I did have a sore on my lip that appeared about 85 days post exposure, looked somewhat like a pimple. It now looks like a small red bump. 

Are these syphilis tests fully conclusive? Would you still recommend a test based on the appearance of a rash? The rash varies in intensity during the day, if I'm lying down for any period of time it isn't visible at all. I have had similar feeling "rashes" before. There is also a heatwave here at the moment and I had my Janssen vaccine 7 days ago, both of these events coincide with its appearance. 

There is a syphilis outbreak here at the moment, but 91% of cases are amongst men, and my sexual partner was female. 

1) With the above information, would you still advise a syphilis test? 

2) As I have had a negative syphilis test and negative HIV test at 99 and 119 days post exposure, can I put the possibility of either infection behind me? 

3) Can I safely resume unprotected sex with my regular partner? 

4) What is the window period for syphilis EIA (igG/igM) tests? 

5) Is there a possibility that 7 days after receiving the Janssen covid vaccine, that the resulting production of antibodies could cross-react with either a syphilis or HIV test and cause a false positive? 

Just to add I have also tested negative for chlamydia and gonmorhea well past the 2 week window period. 

2,3) Repeated questions, addressed above.

5) There are no medications or medical conditions that interfere with the HIV tests you had, and probably none for the syphilis tests. The COVID vaccines certainly do not do so.

We address HIV and STD symptoms, and we now know your rash is neither. I have no further comment or advice about it, except (as noted above) to see a doctor if it continues or you otherwise remain concerned.

Don't overthink all this. This situation is simple and straightforward. You're not going to be the first person in history with HIV in the face of such negative tests!

I appreciate all of your responses, Dr. 

Just to put my mind at ease and for the final time:

1) Do my negative HIV results prove that it is certain I did not acquire HIV from the exposure outlined above? 

2) Do my negative Syphilis results prove that it is certain I did not acquire Syphilis from the exposure outlined above? 

3) Is there a need for any further testing relating to this exposure? 

4) No matter that 'symptoms' I am experiencing now or in the future, there is no way they are related to the above sexual exposure? 

5) As the only unprotected exposure I had was receiving fellatio and performing cunnilingus, was there ever even a risk of acquiring HIV? 

That completes the two follow-up exchanges included with each question and concludes this thread. I hope the discussion has been helpful and that you will move on with no further worries and no furter tests for HIV or any other STI. Best wishes and stay safe.