“If you have a reason to suspect a possible infection of yourself or your sexual partner(s), it is wise to take a test.
We advise you to wait 3 months before you do a test because although most people will manifest antibody levels
within 30 days, a significant percentage do not show these anti-bodies until about 90 days. The National CDC has said
that in some rare cases, it may even take up to six months for one to be tested positive. At this point, the results will
be 99.9% accurate”

So it seems the window period is a must for confirming HIV. You can read up more from the site if you want to: http://www.hivtestlab.com

In many people, the antibodies which HIV tests look for in the blood are present a month after exposure, testing at this time will give a result over 99.8% accurate. Then a patient is advised to get tested again at 3 months which will give a result over 99.9% accurate.

Obviously no test is 100% accurate all of the time, but if you take a HIV test you should be pretty confident that the result you get is correct.

The CDC even states it is best to continuing testing at 3 months, 6 months and even up to 1 year after a possible HIV interaction. Diligence is testing is the solution while the CDC and other labs continue to perfect testing abilities. The tests they had a few years ago don’t even meet the standards of most testing done now adays.

This was in 2005 – "…the use of repeatedly reactive enzyme immunoassay followed by confirmatory Western blot or immunofluorescent assay remains the standard method for diagnosing HIV-1 infection. A large study of HIV testing in 752 U.S. laboratories reported a sensitivity of 99.7% and specificity of 98.5% for enzyme immunoassay, and studies in U.S. blood donors reported specificities of 99.8% and greater than 99.99%. With confirmatory Western blot, the chance of a false-positive identification in a low-prevalence setting is about 1 in 250 000 (95% CI, 1 in 173 000 to 1 in 379 000)."

Nothing in life is fail safe, nothing in life is 100% accurate expect for birth, death and taxes. By testing standards today, along with diligence and following the guidelines/window period through testing can we continue to see if patients are positive and negative.
It is with any type of test out there; from condoms, birth control and other STD testing. Nothing is 100% accurate but you can rely on better testing now than you did years ago. Even the NAAT testing for Chlamydia and Gnorreahra is currently at 95% when three years ago it was between 60% – 80% accurate.

"Other studies have confirmed the accuracy of current methods of HIV testing in the United States, reporting false-positive rates of 0.0004% to 0.0007% and false-negative rates of 0.003% in the general population."

If you wanna be a denialist and put everyone in a tizzy because you think it’s stupid to test, do it on denialist websites instead of being pesimisitc that nobody in life can give you 100% all the time. It’s life, deal with it.