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Avatar universal

reliability HIV test

First I want to thank medhelp in general and Professor Handsfield in particular for the excellent service provided on this website. I live in Western-Europe and have the following concern:
I three months ago was exposed to a potential HIV risk when during intercourse with a sex-worker(female)the condom slipped off and was only noticed a couple of minutes later. At 11 and 13 weeks I took an Elisa/Western Blot test and they fortunately turned out negative. I know from FAQ that this is considered to be conclusive and final testresult regarding detectable antibodies. However I noticed that some experts say(e.g. Mark H. Katz, M.D. Regional HIV/AIDS Physician Coordinator
Kaiser Permanente of Southern California: "A negative ELISA at 13 weeks is reasonably conclusive, but most references state that a small percentage, less than a fraction of one percent, can turn positive between 3 and 6 months")or describe in their medical handbook 2003(Hopkins institute) that some cases DO seroconvert between 3 or 6 months. My question is should I be concerned(or anxious again?)to be retested in three months or are these very rare cases and can you state your own professional opinion concerning the volume they occur; a fraction of a percent or one in a million etc?
19 Responses
239123 tn?1267651214
I agree with the information you quote from Dr. Katz; that is no change from what this site always has said.  However, I never recommend further testing beyond 3 months for people who have such low risk exposures as yours, and who have no symptoms or other evidence to suggest HIV.

Do the math.  Assume a 1 in 1000 risk of infection from the exposure you describe, if your partner had HIV.  It's probably less then that because of the brief exposure ("a couple of minutes").  Now let's say there was a 10% chance your partner has HIV.  Now let's assume there is a 0.1% chance (1 in 1000) that your 13 week test missed HIV even though you are infected.  To calculate the chance you have HIV, multiply the risks:  0.001 x 0.1 x 0.001 = 0.0000001.  That's 1 chance in 10 million.  In the United States, the lifetime risk of being struck by lightning is somewhere around 1 in 28,000, or 357 times higher than the chance you have HIV.

Bottom line:  Don't worry about HIV from the exposure you describe.  You're home free.


Avatar universal
Unless you had gone through courses of chemo treatment, or been a LONG term drug user, or you immune system was SEVERLY DAMANGED (which if it was I doubt you would be sitting here right now), or you had another encounter since..... I think your 100% conclusive.
Avatar universal
thanks for the reassuring message; it will certainly take away my anxiety. although statistically in my case it would not make a significant difference i would like to say that in western-europe many times a potential hiv transmission rate from f/m intercourse is defined as 1:100 instead of 1:1000. but I am very relieved to hear that the bottomline is that I am homefree!!
239123 tn?1267651214
I am unaware of any data showing that heterosexual transmission in Europe is any more efficient in Europe than in North America.  For Western Europe, I would expect the opposite to be true.

On average, transmission risk may be higher in eastern Europe, especially the Balkans and former Soviet states; and it is higher in Africa. This is because overall STD rates (important in enhancing HIV transmission) are higher in those locations, and because in general the HIV epidemics are at earlier stages--so that more people have recently acquired infections, when viral load is high.  But in Western Europe, these factors actually would imply a lower risk of heterosexual transmission than in N. America, not higher.

Avatar universal
Dr. H,

Circumcision plays a BIG role in tranmsission, right?  The foreskin actually facilitates transmission.  But, when it's cut off, skin forms a sort of protective layer (since the virus can't pass through intact skin).
239123 tn?1267651214
The increased risk of cacthing HIV is roughly double in uncircumcised men, other things being equal.  Even with substantially lower rates of circumcision in Europe compared with N. America, it doesn't come close to explaining the tenfold difference (1 in 100 vs 1 in 1000) cited by bealus.  

Avatar universal
With all respect and with all that I (and we all) owe to Dr HHH I must say that I sometimes find the information on the window period inconsistent. While I understand that the closer we get to the day of exposure the less sure we are about the reliability of the test so we say 98%-99% or may be 99.99% at 6 weeks etc. Then Dr HHH says 100% at 13 weeks im most his posts and that the 6 months delay is "out of date" with modern tests etc. And then you sometimes are presented with the "let us do the maths" approach where the risk that the test does not catch the virus at 6 weeks can be assessed at may be 1% may be 0.1% and (depending on the day the question is asked) again that the risk that the test does not catch the virus at 13 weeks can also be 1% or 0.1%. yes I have have been observering a rather random way of choosing the ratios in the "let us do the maths" calculations and yes these differences do matter both from the public health and personal point of view - imagine 1% of however many millions that are doing the tests each year in your country are not caught by the test even if the share of infected is low. and from teh personal point of view whether the risk of 0.1% that the virus is not caught by the test is low or high is very subjective. Some might say that with a deadly virus like HIV that we could pass to our lover ones this risk is pretty low. And yes 1 in 10 million can be considered high enough by some even if the "lifetime risk of being struck by a lightning" is higher (btw the such concept of lifetime risk of being struck with anything is not very illustrative since in our lifetime we are going to be strick with sth with probability of 100%). Finally I (and i think many others) have a problem with conditioning teh advice about the tests on the type of exposure. type of exposure is one thing and the reliability of the test is another thing even though the risk of being infected despite the negative tests is obtained as a combined probability. While I understand one may be a bit vauge about 6 weeks i really do not understand why we are being equally vague about the 13 weeks now. After all most agnecies now agree with the 12-13 week period and the cases of seroconversion after 3 months are very few, not very well documented and date back quite a few years ago. So why are we not keeping things simple accodring to Dr's KISS principle? Why I have an impression that there pretty much doubt about reliability fo 6 weeks test as there is about 13 weeks test? Why go through all the trouble if there is so much uncertainty? It seems to me that European agencies (for what they are worth) keep things simpler - tests are very much standardised and teh advice is very much standardised with 12-13 weeks being as close to 100% as we can get. No one talks about 6 months anymore apart from adressing the anxiety of people who have seen 6 months on the few American sites that still mention it (for what reason?). So what is the simplest story we can get DR HHH? For the moment the similicity of the story seems to depends on the day the question is being answered. is this as close to KISS principle as one can get?
Avatar universal
yugo reading your comment there are some points of view that to my opinion make sense:
the reliability of a test itself should not be related to the
"grade" of exposure; if a test is reliable it should detect after say three months a high risk exposure as adequate as a low risk exposure. for risk-assessment purposes you can of course combine the two aspects especially when you test before the defined window-period has been reached.
i indeed too notice a striking difference regarding the 3 or 6 months window-period; while many western european countries see the 6 months testing period as obsolete many american medical websites stick to it, maybe due to legal reasons or still following the guidelines from the american CDC which date back to 1985.
From the website aegis.com/askdoc I may quote an answer given by Lisa Capaldini, M.D. and associate clinical professor at California University S.F.,that sounds consistent:
"The source of the confusion is this: the older HIV antibody tests DID have a 3 to 6 month window period during which an HIV-infected person might not have made detectable antibodies: hence we recommended testing up to six months post-exposure.
The NEWER antibody tests are typically positive within 4-6 weeks, and with these newer tests the 6 month window is no longer relevent. So to answer your good question, yes, I have seen people go from HIV negative to positive between the 3 to 6 month period with the OLD test- this type of delayed antibody reaction is NOT characteristic of the newer tests in use now, so file the retest at six months is the HIV historical practice bin"

Avatar universal
the thing is that on that same website aegis.com/askdoc  you can also see other docs friendly advising to test at 6 months... :) very inconsistent and (having read what i have read for the past 3 months) I cannot help to think that these guys are just mechanically repeating the 6 months that they have heard somwhere sometiems may happen - it does not cost them anything to say that you should be testing every 3 months for the rest of your life - surely you cannot argue that this would not further marginally increase the accuracy of the test - but it is you the patient who is paying for it emotionally. i think i have decided I do not believe the 6 months BS. But am a bit disappointed with the volatility of DR HHH's statements - he has almost convinced me about the 6 weeks window but on some days his posts make me question even the 3 months window... this is a bit upseting. but may be indeed it is our repeated questions that are prompting this. Still, if it was me and I had a professional opinion I would repeatedly and stubbornly repeat: 6 or 13 weeks for a conclusive result, move one with your life, full stop! - according to the KISS prinnciple- it would save us all time and worry.
79258 tn?1190634010
I think that your anxiety is causing you to read MUCH more into his responses than is warranted, and to thus interpret his advice as fluctuating. However, it's actually quite consistent. Dr. Handsfield has repeated the reasoning for his advice a number of times; you may want to read back over some older posts if you're interested. But in a nutshell, his advice is generally based on actual risk. If you were the receptive partner in unprotected anal with a known HIV positive partner, certainly you were at higher risk than 99.9% of any of the posters here - most of whom are at theoretical risk of HIV transmission only. I suspect he'd suggest the former get tested at 3 months, while the latter is certainly fine at 6 weeks.

Dr. Handsfield has also recently addressed the issue of inconsistency between sites. Read back a few days for more info.
Avatar universal
hi, monkeyflower
well, I have been a very keen reader of this forum for the last three or so months even though I would prefer to never have gotten myself into the situation that led me here. Sure, i am anxious but to some extent my anxiety is fuelled by the conflicting info. This forum is probably still among the most consistent ones and I have had the most comfort and information in what Dr HHH is saying and the way he is saying things.

Still, and I am satying this out of sympathy for DR HHH and thsi forum, when I read

"I agree with the information you quote from Dr. Katz; that is no change from what this site always has said. However, I never recommend further testing beyond 3 months for people who have such low risk exposures as yours, and who have no symptoms or other evidence to suggest HIV."

and in another one I am reading

"13 weeks is conclusive regardless of route of exposure"

then anyone (not just anxious Yugo) stops and thinks 'well, all very well but these two statements are contradictory' this is because the first statement implies that there are some exposures for which Dr HHH would recommend further testing.

Now from a personal point of view the degree of exposure risk does not matter (!!!) because we are concerned about our health and very often about the health of people that we love. hence whether I had an anal conatct with a positive person or any other contact with person of unknown status I want to make sure I have done all I could not to put others at risk. So if 3 months is not any better than 6 months test for a normal person it should be simply said: 3 months is as good as it gets, period, move on. And this is what DR HHH says most of the time but then you read that perhaps there are some exposures for which even normal people would be advised to test at 6 months. And this causes ANXIETY.

all the best,
Avatar universal
Dr HHH, I do appreciate your advice--I am getting there. Keep up the good work that you are doing - it is very important for a lot of people. Best
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