[Question #322] duo tests accuracy

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102 months ago


I’m a heterosexual female from Prague, Czech republic (Central Europe). I had an unprotected vaginal intercourse (probably for a couple of seconds, before I told my partner to put on a condom) and an oral sex with someone I didn’t know that well. It was my first sex ever. About 6-7 days after exposure I had a fever for one night and then a temperature the other day, altogether with a headache, fatique and muscle pain. The fever/temperature, headache and muscle pain lasted for approx. 1,5 days, and for a few couple of days I was just tired and probably had some swollen lymph nodes.

I had an HIV duo test (for p24 antigen and antibodies) about 7 weeks later (52 days), and it was negative. I accepted the result and was calm for a while, since I’ve read on the internet that duo tests should be conclusive 4 weeks after exposure. But then I started thinking about it again, because I’ve realized that I’m not sure if the information I’m reading online about HIV duo tests can apply to my country, since the official guideline for when  HIV duo tests are conclusive is I think 8 weeks in my country.

So I have the following question:

Is my 52 days negative test conclusive? That means is the HIV duo test conclusive after 4-6 weeks everywhere in the world, or more precisely everywhere within Europe and North America? Is it possible that a duo test done in the Czech republic is conclusive later, for example after those 8 weeks, for example because the testing method is different or the „testing machines“ older (not really sure how it works)? From what I’ve learnt online, the tests should be everywhere the same, but I’m not sure. Btw my HIV duo test was done at probably the best institute where you can have the tests done in my country. 

Thank you very much for your help!

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H. Hunter Handsfield, MD
102 months ago
Welcome to the forum. Thanks for your question. I'm sorry to hear you are so concerned about your first sexual encounters. But truly, you need not worry. They sound like safe encounters with partners who probably are unlikely to have HIV.

The duo tests are the same throughout the world, and there is no reason to fear anything different in the Czech Republic. What you learned online is correct:  all laboratories purchase the test kits and machines from the same companies, and there is no such thing as an older machine that would give different results. The duo tests are conclusive any time 4 weeks or more after the last possible exposure. If the Czech government or public health authorities say 8 weeks, it is because they are being careful and conservative. I have never seen or heard of any patient with negative duo test at 4+ weeks who later turned out to have HIV. In any case, there is certainly no difference in test performance between 52 days (7.5 weeks) and 56 days (8 weeks).

Because the HIV blood tests are so reliable, the results always overrule both exposure history and symptoms. As noted above, your sexual exposures were low risk. And your symptoms started and ended too soon. HIV symptoms don't start before 7-10 days and last at least 1-2 weeks. It sounds like you had a common respiratory virus. In any case, it would not matter even if you had a very high risk exposure or typical symptoms: the test results tell the truth.

Therefore, you don't have HIV. If not tested for other STDs, that also might be a consideration, i.e. syphilis blood test and vaginal swab or urine testing for gonorrhea and chlamydia. But these risks also were very low after only the two, brief exposures you had.

I hope this has been helpful. Best wishes and stay safe!


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102 months ago
Dear Dr. Handsfield,
thank you so much for your answer, it was very helpful.
Best wishes, Karolina