HIV Prevention Community
52.8k Members
Avatar universal

window period data?

Hi everyone,

I was wondering if anyone has seen any real data on the window period question? Maybe studies of seroconversion times, etc. I am still very confused and somewhat upset about the uncertainty out there. I did call the Mass state hotline and they tell everyone that the window period for a conclusive HIV antibody test (independent of test generation or kind of test btw) is 6 weeks. In their view, the CDC is being tooo conservative and only people with suppressed immune systems would take longer than 6 weeks. Now the CDC will say that 3 months is conclusive and that people with weakened immune systemms might in fact take 6 MONTHs to convert. ANd the guys on the aidsmeds forum are sharing that view (some of those folks are misinformed about the Mass guidelines btw and state test performance as a reason for the inconsistency which is NOT the case).

The counselors on the Mass hotline say that the state has the exact same data and the exact same tests as almost everyone in the US and that their conclusion is that 6 weeks is more than enough time for a conclusive result.

So then why does the CDC still recommend 3 months??

Did anyone actually see any data/studies? I know Dr H repeatedly said that the exact experiment on thsi will never been done for ethical reasons and I buy that. But what data are the window periods out there based on then?

31 Responses
Avatar universal
Avatar universal

The window period is a tricky subject, and when we consider it, we have to take into account the likelihood that any one person may have contracted HIV from the encounter that has them worried.

It may help to think about it in terms of odds, C, because the business of calculating the window period is not an exact science. Let's talk about that first and then go back to the odds discussion.

I am sure that you have heard that most people will develop antibodies that may be detected on an HIV test within 25 days. OK, if that's true, that means that the average time to take an HIV test after a possible exposure is 25 days, or roughly 3 weeks. However, notice the term "most", which naturally implies that not everyone will develop antibodies by 25 days, but most will. How then do we capture the outliers? If we tell people that 3 weeks is sufficient, how about those handful of people every year that develop them at 4 or 5 weeks? What about them?

The answer is, take the average and pad it a bit. Slap another 3 weeks on there (as some do, to arrive at 6 weeks), and call that the time to definitive test. That seems reasonable to me. So, a vast majority of people (the number of average progressors plus those that may take just a little longer) will turn positive by 6 weeks.

Still that qualifier, though: vast majority. What's up with that? Well, there are a handful of people who may acquire HIV in any given year who take longer to develop detectable antibodies than 6 weeks. Who are these people, and are you one of them? Before you start thinking that you are, let me say this: if you don't know that you are, you aren't. If you were, you would surely know it. Why? Because, the people who fall into this category are not your average bear - they are people with severely compromised immune systems. Chemotherapy patients, for instance. They aren't in good shape to begin with, and nor are their immune systems, so it doesn't really come as any surprise that their bodies cannot mount a response to an HIV infection. And when I say not in good shape, I don't mean that they feel a little bad each day, or that they have the sniffles, or that they are on some medication. No, I mean they are laid up in a hospital bed or are in some other dire circumstance. Clearly not you.

So, we have this very small percentage of people who may take longer than 6 weeks to show antibodies. What do we do? Or, rather, what does the CDC do? They say wait until 3 months, and they say for everybody to wait until three months.

At one point, the CDC said to wait until 6 months. But, clearly, the tests available, or the testing data itself, had advanced to the point where it was recognized that 6 months was outdated, and the window was revised down to 3 months. And I am willing to bet that at least a while before then, ID specialists in the field were telling their patients, men and women just like you and me worried about HIV, that a 3 month test was sufficient. In other words, as a doctor once told me, the CDC invariably will lag behind the accumulated convential wisdom being established every day in the real world. And there may be a good reason for that. They are in a tricky business, after all, so perhaps being conservative is a good thing for them. It is, of course, frustrating to hear one thing from them, one thing from someone else and then another thing from another person. Makes it seem a bit, well, chaotic. But, that is sometimes the nature of medicine. We want to believe that our doctors know everything, that everyone is in agreement - but it often doesn't happen this way in any scientific field, let alone medicine.

My belief concerning the CDC's version of the window period is that, as other organizations start revising downward, they will eventually follow suit. Can't say that for sure, just my feeling.

Now, a discussion of odds and how they relate to when you should test, or if you should test. It can be boiled down to odds: what are the odds that a person's behavior has led them to contract HIV? And, based on an assessment of those odds, or the risk that someone has contracted HIV, when should that person test, or stop testing?

For instance, let's say that you, as a male, receive oral sex, protected or unprotected (as far as I can tell, the odds are the same - zero) from a woman of unknown HIV status. When should you test? Well, if you look at the odds, let's say that there was a 1 in 20,000 chance that you may have contracted HIV this way (and I should caveat this by saying these are theoretical odds, because no one has ever contracted HIV from receiving fellatio, but, for the purposes of this example...). Most doctors would say forget testing altogether, but, if it you would make you feel comfortable, get a test at 6 weeks and call it day. Why 6 weeks? Because, the odds were so overwhelmingly against you having gotten anything in the first place, if you test negative at 6 weeks, the odds would be astronomically against you having gotten HIV.

You might be saying, wait, I thought the test was definitive, as in, 100% you don't have anything at that point. Well, if you look at it logically, that's really what it is. If I told you that there was a 1 in 20,000 chance that you were going to be hit by a meteor tomorrow if you left your house, what would you do the next day? Think about your answer carefully. Me? I wouldn't think twice about it, because those odds are overwhelmingly in my favor. You have a 1 in approximately 250 or so chance of dying in a automobile accident in your lifetime. Do you not ever get in a car? Now, what if I told you that there was a 1 in 500,000 chance that you had HIV after that 6 week test? What would you do then? I bet you wouldn't sweat it so much, especially if you consider there is a 1 in 76000 chance that you'll be killed by lightning in your lifetime. This is what it means when any doctor tells you that the chances are so low as to be not worth worrying about. Truly they are. And for most posters on this and the moderated forum, that is the situation.

Of course, there are riskier situations that one may put oneself in in terms of potential risk of contracting HIV. Consider a nurse working in a hospital. She draws blood from another woman known to be HIV positive. In the course of capping the hollow bore hypodermic, she sticks herself deeply with the needle. What happens then? The odds are much greater than usual that she may have contracted HIV, though, surprisingly, the odds are still decent that she didn't.

Having said that, given the situation above, after a 6 week test, my bet is that she is going to breath easier, but her doctor is still going to want to test out a bit longer. As I said, she still has good odds, but, just to be sure and extra cautious, might as well go out to 3 months (and maybe even six, though don't know that for sure).

I know this is the longest forum post ever, but something else to consider and then I will call it a night. Our perception of the odds that we may have been at danger of contracting HIV are, in most cases, highly skewed. A common theme in this and the moderated forum is to perceive our odds as much higher than they actually were or are. In other words, a vast number of the posts describe situations that weren't really all that risky to begin with. HIV is not a a very easy virus to catch.

Believe me, I know how hard it is to be logical and calmly objective when going through something like this. But keep in mind, the odds are with you.
Avatar universal
Avatar universal
xhost... Thank You! For someone like myself waiting to get tested, your post helped my anxiety drop(plunge) Thank You!!
Avatar universal
The subject matter is somewhat cloudy because of the fact that studies are not done to measure it. In a study people would need to be infected and then studied, insuring that there was no possible HIV contact after the infection date and this sort of study will not be done, not even on volunteers. The window period guidelines are from historical observation of the epidemic. Also keep in mind that the vast majority of people who become infected do not know when they were infected for certain. Therefore, the first time they test positive gives us no insight into the window period at all.
Avatar universal

I think Ronnie has a good point. It's not as if any doctor is going to deliberately infect a group of people to determine when they show positive on a test. Much of what you see in the literature concerning the window period is based on "best guess" data.

It seems, though, that many people who talk about time to the average positive test, are fairly definitive in saying that about three weeks and a couple of days is the average.

You will certainly read stories from people who say that they tested positive after 6 weeks, though on the sites that I frequent, HIV workers and doctors say that they have never seen this happen. So, one questions the self reporting nature of stories one reads on the Internet, which can include all types of things: time to positive test, mode of transmission, etc.

In the end, it comes down to who do you trust. It so happens that I came to trust the doctor on this site (Dr. H, who moderates the HIV Prevention forum), and thus I tend to follow his line of thinking.
Avatar universal
Keep in mind also that, at least in my non-medical opinion, you can pick up other bugs from a sexual encounter, other than HIV or other known STDs. Just because you feel bad/ill after a sexual encounter does not mean either you have HIV (or another STD) or you are a nut-job. There have to be other causes/alternative explanations. I know what happened to me and the tests say it was not HIV or another known STD. It might have been EBV, but whatever it was made me horribly ill in a long term sort of way. I had swollen glands all over, even above my ears early on and I have never felt well since almost a year later! Keep in mind that I was always a healthy person before. I only had less than 5 sick days in over 10 years at work.

HIV, EBV, CMG, HPV, there are a lot of viruses out there that can bring you down!! Don't fixate on HIV. Listen to what the test results tell you. If the test says negative out of the window period, then accept it and work on getting your rest, exercise and feeling better!!!!
Avatar universal
i actually got tseted after 3 weeks,  it was negative but im worried about all that window period ... what is the percentage that it could be positive, ???  like i read nonone had seen taht but hter is a chance i really want to know, im worried you know, im still on 4 weeks since all happend. so .... ofcourse i don' t know, could you tell me me if it could be positive? in 2 weeks? i
461503 tn?1212069610
The CDC, WHO, UNAIDS, Europe guidelines, says that the window period is 12 weeks, this is becouse they have to be very conservative on their guidelines, and becouse not all the testing facilities has the same generation test or not all use aproveed test, for an example in Australia the window period is just 6 week, this is becouse all their testing facilities has 3rd and 4th generation test, and only a few but very good aproveed tests, so until all the testing facilities around the world has and stadarization of tests, is not probable that the guidelines will change to the 6 week window period, you can find figure of the window period regarding each kind of test on this link, and this comes from ROCHE that is one of the biggest medical industries and that propably have more scientist working there that in the CDC

Avatar universal
I'm a little skeptical on the 3 month guidline. The Doctors say most high risk people couldn't state when their risk was. The data in the epidemiological studies may be based on the last reported risks of all the individuals.Who knows, the majority of actual infections may have taken place before the last possible risk skewing all the datasets to a shorten window period. Then again perhaps not.

BASHH in their guidelines have a disclaimer or two:**Observational data are limited** [References 8-14], but in ten years of application of the 'three months rule' by all members of the UK HIV Laboratory Forum no reports of its failure have been received, and thus it is recommended that ***in general*** the three month rule continues to be applied 15. [Reference IV C]

The Health Protection Agency also leave it to the discretion of a clinician whether to test out past the 12 week *guideline*.
Avatar universal
Health Protection Scotland said 6 months 'just to be sure'.
A couple of GUM clinics said if the person is known positive then testing out to 6 months might be appropriate.
Avatar universal

Yeah, Thats what they say in Canada.... 6 months to be sure.
But with what I;ve learned on this forum.  if you are 12 week neg, then move on....
Avatar universal
Xhost has hit the nail right on the head.

In Australia many labs stop testing at 6 weeks, Massuachusetts agree with it and so does Dr HHH and Dr Ewh

Most of the 4th generation tests detect HIV as early as 2-3 weeks and 6 weeks is a kind of padding to be on the safe side to detect the vast majority

See this chart from the VIDAS duo manufacturers , which is claimed to be the most sensitive:
Avatar universal
is orasure oral swab 4th generation?
461503 tn?1212069610
No is not a 4th generation test
Avatar universal
then what generation test is it?
461503 tn?1212069610
I couldnt find what generation it is, you can contact orasure and ask them, but they said that window period for their test is 3 months,
Avatar universal
ok, thanks, on Baller's behalf; when I tested yesterday,with Oraquick, the lady said, one mont is very encouraging. So does that mean it is as realible as as ELiza?
Avatar universal
yes in my case when I tested at 6.5 weeks also the lady who did orasure said it could detect if there were antibodies at this time. Is this true?
461503 tn?1212069610
Orasure is as good as any elisa for negative results.
Avatar universal
A 4th generation test is a 3rd generation ELISA with an antigen detection layer.

If anything the Antibody detection is slightly less sensitive on a 4th generation than in a 4rd generation.
Avatar universal
you meant to say 3rd generation?
Avatar universal
Thanks, and can you please reply to my e-mail about my lady friend. I appreciate this.
Avatar universal

The above chart says any 3rd generation can detect infection from 5th weeks? any one can commment pls.

Have an Answer?
Top HIV Answerers
366749 tn?1544698865
Karachi, Pakistan
370181 tn?1428180348
Arlington, WA
Learn About Top Answerers
Didn't find the answer you were looking for?
Ask a question
Popular Resources
These tips can help HIV-positive women live a long, healthy life.
Despite the drop in new infections, black women are still at a high risk for HIV, the virus that causes Aids.
What are your HIV treatment options, and how do you choose the right one? Our panel of experts weighs in.
Learn the truth behind 14 common misconceptions about HIV.
Can HIV be transmitted through this sexual activity? Dr. Jose Gonzalez-Garcia answers this commonly-asked question.
A breakthrough study discovers how to reduce risk of HIV transmission by 95 percent.