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Window Period Info from the CDC -- Please Post
Feb 15, 2003

Dear Dr. Bob,

As my 4 year old son would say "You're awesome man!!!" You are literally a superman of doctors.

Thought some of your fans might find this information useful if not comforting.

I have had the SUDS rapid test done a couple of times and have looked up some information on rapid tests on the CDC site. While looking at the information that the CDC provides, I found some information on the window period that should provided some comfort to everyone concerned about the window.

If you look at the CDCs guidelines for CTR (counseling, testing, and referral), they say (I'll paraphrase) "that if you are tested at < 3 months the test will not be definitive since enough time may not have elapsed to develop detectable antibodies. Testing would be recommended at >= 3 months. If the result is negative at > 3 months, the client is likely not HIV infected. If client or provider concern remains or if the negative result at 3 months is incompatible with the clinical history, then testing can be repeated at > 6 months." Many of you who have called the CDC hotline also know that they staunchly adhere to the 6 month retest rule. This has been very frustrating to me and many others since this information leaves so much ambiguity.

When you look at the information on rapid testing on the CDC site (an official CDC document), they do not even mention 6 months. I have cut the following paragraph directly out of the CDC page:

FROM THE CDC site ( ==============

What are the limitations of the test? Does this test always give a correct result? =========================================================

No test is perfect there may be a very small proportion of people who are not infected with HIV who will have a reactive result on this test (false positive), and a similar small proportion of people who are infected with HIV who will have a non-reactive result (false negative). Also, this test will not detect HIV infection in people who are tested within about 3 months of exposure to the virus (3 months is the time it takes for detectable antibodies to appear in the blood in response to the HIV infection). These limitations are true for all currently approved HIV antibody tests. For these reasons, it is essential that all individuals who are tested with this rapid test be appropriately counseled both before being tested and after receiving their test results. For those individuals with reactive test results, follow-up testing using another technique is necessary to confirm that the result is positive for HIV antibodies.


Here is more information taken directly from the CDC site (

More info directely from CDC ====================

Negative Rapid HIV Test Results

During the initial visit, the provider can definitively tell clients whose rapid HIV test result is negative that they are not infected, unless they have had a recent (within 3 months) known or possible exposure to HIV. Retesting should be recommended for these clients because sufficient time needs to elapse in order before antibodies develop that can be detected by the test.


End CDC site information

Notice that they do not say to come back in at 6 months... They say "During the initial visit, the provider can definitively tell clients whose rapid HIV test result is negative that they are not infected, unless they have had a recent (within 3 months) known or possible exposure to HIV. " I really don't believe this is just because they were sloppy with their information, I believe that 3 months is really the time that will give you a definitive answer.

Please also notice that they mention that these limitations apply to all FDA approved tests for HIV antibody tests and not just to rapid tests.

I am sorry for the long message, but I hope that this will put some minds at ease.


P.S. Here are the websites if you want to verify the information for yourselves:


Response from Dr. Frascino


Thanks for writing. And, I couldn't agree more. The only caveat is that if someone had a very significant exposure, such as unprotected anal receptive intercourse with someone known to be HIV-positive, or a healthcare worker sustained a deep puncture wound from a needle used on a patient known to be HIV-positive, then a repeat test at 6 months (if the 3-month test is negative) is warranted. Thanks for doing the thorough research and providing the websites. I'll bet you wrote one helluva good term paper writer in college, now weren't you?

Thanks again!

Dr. Bob

young and scared

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