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Window period for DNA PCR
#136799 - 03/06/05 12:34 AM
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Greetings,
I had possible exposure to HIV 3 weeks ago. In a week's time I am leaving for a place that doesnot have any discrete HIV testing facilities. I am tempted to go for a DNA PCR test.
It would help a lot if you can tell me what is the actual window period for a DNA PCR test. I have been told a whole lot of figures - right from 72 hours to 30 days. What is the correct - minimum period one should wait before getting a DNA PCR ?
Also, can a 4 week new-gen ELISA be treated as conclusive ?
I had unprotected anal sex with a low risk individual. I was the insertive partner. The episode was even more low risk because I could never achieve proper/full penetration.
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Low risk individual? Anyone who is allowing you to have unprotected anal sex with him, I would question whether he is "low risk". Anyhow, PCR testing is considered accurate at 28 days however is not intended for HIV diagnostic purposes. Conclusive, definitive testing can be done 13 weeks post exposure with an ELISA test. The fourth generation test will not be conclusive, but it would be a good starting point to ease your mind.
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Anonymous Coward
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Thanks for replying,
I get your point about "low risk". The individual concerned has only had unprotected anal sex once before. His relativily inactive sexual life made me classify him as "low risk".
Can you elaborate on what you mean by DNA PCR is accurate but not intended for HIV diagnostic purpose ? You mean govt. agencies recommend ELISA and not DNA PCR because of it's cost even If DNA PCR has a lower window period - or - is there a technical reason for not having/trusting a DNA PCR test ?
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At 28 days the dna/pcr test is the best test in the world. Forget all the not approved tripe that's al about money. If you are Neg on the pcr test at 28+ days you do not have hiv infection
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The problem with a PCR is that it can give a false positive result. You can't however, get a false negative. Just depends on whether you want to take the risk? For me I would rather wait out the window period to be absolutely sure.
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Get tested together with your sex partner today not tomorrow for human immunodeficiency virus and other sexually transmitted infections or you get tested today yourself. If another test later detects something that was not detected today it gives a time frame that will make it easier to determine treatment.
See also a collaborative blog about the strategy
get tested together before you have sex
http://NotB4WeKnow.EditThisPage.com
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Does this 28 day period have a built in buffer ? My problem is I am leaving for elsewhere on my 28th day from possible exposure. What if I get a DNA PCR on the 25th day ? Would that help ?
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Hi, I agree with the other responders. The DNA-PCR is not as sensitive as modern serologies at the three month mark (the Johns Hopkins Guide indicates a maximum of 99% analytical sensitivity, in clinical practice the sensitivity is often a little lower). It has a much higher tendency to produce false positives than statndard serology. Moreover, the commercial Roche DNA-PCR-kit most widely used is mostly sensitive for HIV-1 subtype B. Even with the Roche 1.5 primers, there are subtype problems. So the baseline is that such testing should only be done in cooperation with an experienced infectious disease doctor with long-term experience with testing in the window period. You will have to test at the 3 months mark anyway. Take care and don't panic!
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This statement needs refinement. There are indeed examples of false negative DNA-PCRs. A 3-6 months serology is probably substantially less likely to produce false negatives. Subtype problems, transport problems (wrong temperature), low levels of integrated provirus or problems with a cumbersome procedure for running the tests are factors that relatively rarely produce false negatives.
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Well I guess that sort of settles it. Will not go for a DNA PCR. Will do ELISA at 3 month mark.
Thanks everybody for responding
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http://www.srlranbaxy.com/news-hiv.htm
This webpage states that their DNA PCR tests can detect HIV-I & II at extremely minute level. So minute that they can be detected 72 hours after exposure ???
Is this for real or just marketing bullshit ??
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For sure bullshit. All such assays have big or small sensitivity problems. Such broad statements have to be corraborated by clinical studies.
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