[Question #3196] HIV Window and Accuracy

39 months ago

I wanted to understand the current window for 4th gen combo/duo tests. I had a significant exposure last year (unprotected sex with a high risk escort). 

My questions:

1) I've had several HIV tests and believed this was behind me until i recently came across one of the links you posted and this was the new findings by CDC. It seems to suggest that 99% of infections are identified by 43 days, does this mean that 1% are identified later? At what point does the CDC believe a person can obtain 100% accurate results?

2) I have tested using Lab Duos in the UK at the following intervals: 35 days, 50 days and 77 days. How accurate are these tests? In the UK, guidelines suggest testing at 4 weeks and then again at 8 weeks only for high risk exposures. I have tested past the 8 weeks so would this be conclusive?

3) I was concerned about the 12 weeks/90 days that is everywhere on the internet so i tested again using a rapid combo available in the UK (Alere HIV Combo) at 84 and 98 days, both negative. Whats the accuracy on these?

4) Based on my exposure history, the tests taken at the intervals etc, is there any need for me to re-test at 6 months?

5) The rapid tests taken at 84 and 98 days, should i have elected for the Lab Duos instead as I've read that these are more accurate/sensitive than POC tests?

6) Rare sub-types, late seroconversion, missed infections, the test not accurate enough - these are the horror stories on the internet. They just add to existing anxiety i know. Can i be 100% confident and finally move on from this episode?


Edward W. Hook M.D.
Edward W. Hook M.D.
39 months ago

Welcome to our Forum. The guidelines for when tests for HIV are conclusive have evolved over time. The current standard HIV tests, including the ones you had (combination HIV antigen/antibody or "duo" tests), are among the most accurate diagnostic tests ever developed, for any medical condition. When done sufficiently long after the last possible exposure, the results are 100% reliable. The antigen-antibody ("4th generation") HIV tests you had are conclusive at 6 weeks. Previously it appeared that these tests were conclusive at 4 weeks (28 days) however a very small number of cases have been reported in which tests did not become positive until between 4 and 6 weeks.  Any continued advice about testing at 3 months or beyond is just being overly conservative and careful. In fact, the CDC scientists primarily responsible for HIV test evaluation recently published a commentary acknowledging conclusive results well before 3 months:  below are links to that commentary as well as a comprehensive review by other HIV testing experts about the performance of the current tests. In other words, your test results were conclusive for all tests beyond 42 days.  Even if you had unprotected sex and even if your partner had HIV, your test results prove you weren't infected.




Thus, in answer to your questions:

1. the 99% figure is overly conservative,  Your results at 50 and 77 days were conclusive.

2.  See above. I suspect your results were truly conclusive at 4 weeks.  The later tests certainly were.

3.  The internet is full of misleading statements.  I urge you to stay off of it for the purpose of getting medical advice.  Your later tested, like the earlier ones, were conclusive.

4.  No need for further testing related to the exposure you mentioned.

5.  The strength of the Duo tests is that hey provide earlier definitive results.  The results of your 84 and 98 day tests are, like the earlier ones, definitive.  It is time to believe them and stop testing.

6.  More internet mythology.  Please don't believe them.  You have proven, repeatedly, that you di not have HIV.

I hope these comments are helpful.  To summarize, you clearly do not have HIV form the encounter you describe.  there is no need for further testing.  I strongly advise you to stay off the internet.  Take care.  EWH 



39 months ago
Thanks for your reply.

Some follow up questions:

1) You say 99% is being conservative, why don't the CDC just state 100% to put people at ease? They are very careful in their wording throughout the site 'most people' rather than saying all people. Who would not develop enough antigen/antibodies to be picked up by 42 days?

2) In regards to Rapid Duo/Combo (Alere HIV Combo) tests - i understand that the antigen sensitivity is not as good as Lab Duos - is this just for early identification? Am i right in thinking that after 12/14 weeks this would pick up the same infections as the Lab Duo?

3) Late seroconversion - is this really an internet myth?! There seems to be quite alot of info out there where reputable doctors have stated it is possible to seroconvert late, is this accurate? I'm currently at 15 weeks post exposure and feel as though I've early signs of the flu (cough, stuffy nose) coming on, could this be ARS now? Could i be a late Seroconverter?

4) Is there a possibility that the Lab Duos at 35, 50 and 77 didn't pick up the low levels of antigen and if i am a late seroconverter that I've also not produced any antibodies to turn positive?

5) I know this is repetitive but i guess my anxiety is taking over. I can't help but think the csw was infected, she offers unprotected sex with all people and if she was infected and in the acute stage at the time of exposure than my risk would go from 1/2500 to 1/133. Than with 99% of infections being found by day 42 that would make my odds around 1/13000 to have being missed. Is there anything else i can do to make 100% sure and move on - take another Lab Duo, PCR etc?

6) Whats your views on the Alere Rapid Combo/Duo after 90 days? Would you have considered this conclusive without the Lab Duos?

39 months ago
Sorry just some more info and clarity to question 3) I’ve currently got a blocked/runny nose with a dry cough. Typical flu symptoms. Neck has started to feel sore, general feeling of run down and tiredness. No fever yet. 
Also worth mentioning my tongue has been white with some yeast at the back. This seems to come and go. I noticed this first after taking a 2week course of antibiotics for a chest infection a few months back. 
Just wanted to give you some more context to my current symptoms before you replied. This has all begun (apart from the white tongue) at 15 weeks post exposure. Could this be late ARS?
Edward W. Hook M.D.
Edward W. Hook M.D.
39 months ago
Straight to your questions:
1.  The CDC is inherently a conservative organization which, unlike this forum, cannot give personalized assessments and which feels it cannot "afford" to ever be wrong.  Thus their statements tend to be rather conservative.
2.  I am not sure where you are getting the your information.  If it is the internet, I would not trust it.  All combination HIV antigen/antibody tests must achieve very similar performance standards for approval.  I am not familiar with a test call the "Lab Duo" test although most combination HIV antigen/antibody tests are typically referred to as "duo" tests.  I am confident at, if approved by the U.S. FDA and WHO, that beyond 12 weeks the results of the test you are referring to provides conclusive results unless you have taken drugs active against
HIV in the interval.
3.  The idea of a "late seroconverter" is an internet myth.  Early in the epidemic with tests used long ago some tests did not become positive until more than 10-12 weeks after acquisition of infection but that has not been the case for more than a decade.  There is no such thing as a late seroconverter so you cannot be one!
4.  No, this is not possible.
5.  Oh please- believe your tests
6.  Believe your test results, you do not have HIV from the exposure you have described.  EWH
39 months ago
Thanks for your prompt response Dr.

Lab Duo = Laboratory performed HIV Duo test on a blood sample. This was conducted at the Doctors Laboratory (well respected Laboratory in the UK).

2) I was referring to an answer given on this forum, that the rapid/instant HIV combo tests are often not as sensitive in early infection as opposed to Laboratory Duo tests. What i was asking was at 12/14 weeks am i to assume the accuracy of the rapid/instant Alere test would be as good/accurate as the Laboratory test?

4) So my current flu/cough etc with white tongue cannot be ARS? I know you say ARS is typically within 2-4 weeks but have you not seen someone with ARS at 15 weeks?

Finally - am i correct in saying with my Laboratory Duos at 35, 50 and 77 days and rapid/instant Alere combos at 84 and 98 days and even with my current flu like symtoms i can safely say i do not have HIV. This is regardless if the exposure was with a HIV+ person etc? 

Any last advice or words of comfort?


Edward W. Hook M.D.
Edward W. Hook M.D.
39 months ago
The symptoms you describe do not suggest HIV.  Early HIV does not cause a runny nose or cough.  

2.  Understood.  The concerns about the very earliest performance of some combo tests have been addressed by the manufacturer and certainly do not pertain to your situation.  I urge you to believe your test results.  They are conclusive.

4.  Please see comments above.  In addition to 15 weeks being far beyond when the ARS occurs, your symptoms are not those of the. ARS.

Please believe your test results.  There is simply no evidence that you acquired HIV from the exposure of concern.  Your results are definitive.

This is my 3rd response to your questions.  As per Forum guidelines, this thread will be closed later today.  Take care and please don't worry.  EWH
39 months ago
Thankyou for your advice Dr and comforting words.

If you could just answer this last question, i did ask earlier but you may have missed it with all the other questions i asked.

What i was asking was at 14 weeks post exposure am i to assume the accuracy of the rapid/instant Alere combo/duo test would be as good/accurate as the Laboratory Duo test? I know CDC say there is not enough research done to call instant Duos conclusive at 42 days and recommend 90 days. So based on that would you consider the Alere Instant/Rapid Combo/Duo after 90 days as conclusive even If i had not had the Laboratory HIV Duo tests that I've had?

Thankyou for all you advice. Really appreciate it.
39 months ago
I know you say that my symptoms are not typical of ARS, just wanted to inform that I’ve noticed the lymph nodes in my neck seem sore and swollen today also. Could this all just be the common cold/flu? 

Happy to pay again to continue the questions. 
Edward W. Hook M.D.
Edward W. Hook M.D.
39 months ago
You do not have HIV.  Paying again would be foolish.  EWH