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HIV TEST AT 14 Weeks?/Canada and U.S.A. testing

Oct 2, 1996

At testing clinics throughout Canada they always reccomend that someone must wait 14 weeks after a possible exposure, prior to being tested. With all the conflicting information could it mean that little is understood about seroconversion? Could you provide me with figures for the number of people who test positive by 3 months if possible?

I'm sorry but being from Canada I'm having a hard time understanding why Canada gives people a negative test after 3 months and the U.S after 6 months. It just doesn't make sense to me...Canadian AIDS hotlines are telling callers that the states is saying that to cover their "butts", I really hope thats not true because unless you've gone through the waiting period for an HIV test result personally you so-called experts just don't understand. If this message sounds very negative I'm sorry but a friend of mine lost 1 year of his life worrying about HIV and to be be honest his biggest mistake was calling the CDC AIDS hotling, had he called the Canada AIDS hotline. He's fine thanks to calling.

Response from Mr. Sowadsky

Hi. Thank you for your inquiry. Most of the confusion about waiting periods for getting tested is due to the fact that there are really 3 time points as to when people show positive on the test.

The AVERAGE period of time that an infected person will show positive on the test is 25 days. This is an average, so not all people will test positive by this point in time.

The USUAL period of time that an infected person will show positive on the test is 3 months. This means that most (but not all) infected people will show positive on the test by this time.

The MAXIMUM period of time that an infected person will show positive on the test is 6 months. By this point in time, more than 99% of infected persons will show positive on the test. This is as accurate as any test in medicine could ever be.

In terms of the accuracy of the test at 3 months, the best statistic I've been able to find is that the percentage of accuracy is somewhere around the lower 90th percentile. It's difficult to get a hard core statistic on the accuracy beyond this lower 90th percentile. The true accuracy may vary from study to study, but if you think about it, even at this level, the tests would pick up the majority of infections. We can say that at 6 months, more than 99% of infected persons will show up positive on the test. So if a person tests negative at 3 months, they're probably not infected, although this would not be considered conclusive. But a 6 month test is the most accurate time to be tested.

Hotlines in the United States mention the 6 month waiting period to take into consideration all realistic circumstances as to when infected people seroconvert. We do agree that most (but not all) infected people will show positive on the test by 3 months. But in the USA, people are also told that taking up to 6 months can realistically happen, although this is not very common.

I know what it's like to have to wait to be tested. I personally have been tested through my private physician, through the local health department, and even by the new home HIV tests. I've taken these tests so I personally understand what people go through when they get tested by all 3 ways. So I know first hand what it's like to have to wait 6 months!

I'm sorry you feel so negative about the American position on HIV testing. But I have to agree with the CDC National AIDS Hotline's position that a 6 month test is the most accurate.

If you have any further questions, please feel free to call the Centers for Disease Control at 1.800.232.4636 (Nationwide). Rick Sowadsky MSPH CDS

Blood Donation Restrictions
Significance of 3 month test

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