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HIV Transmission and Education >> Am I Infected?

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Anonymous
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Accuracy of PCR
      #15250 - 01/30/01 12:32 PM

I have to stop reading some of these posts.

I had a negative PCR-DNA (Proviral) through Quest at 7.5 weeks.

I also had a negative ELISA (3rd generation) at 6.5 weeks.

I've read alot of Dr. H's stuff on PCRs and he says that PCR DNA at 28 days is 99% conclusive and is, in his opinion, the same as a 6 month ELISA (and certainly a 3 month ELISA).

A thought occurred to me...is it possible that one could develop enough antibodies to make the PCR undetectable at 7.5 weeks? The Quest test says it measures down to 10 copies. Do antibodies work that good on the virus that it could bring it down to undetectable levels? That is, are you better off measuring at 28 days, rather than waiting? The folks at Specialized Testing say no...but I don't know who to believe.

Any help out there?



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TexGal
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Reged: 11/21/00
Posts: 139
Re: Accuracy of PCR new
      #15255 - 01/30/01 02:30 PM

I'm sure that anything is possible when it comes to any disease but statistically speaking, it would be unlikely that a DNA PCR would be undetectable at that many weeks unless it was a strain that the PCR could not pick up. (i.e. HIV2 which is NOT prevelant in the US) A DNA PCR in someone confirmed HIV positive with an undetectable viral load should still be positive since the DNA PCR is just looking for the virus itself. It is not concerned with counting the amount of virus hence it is more sensitive.

It is possible but also unlikely that an RNA PCR would be undetectable at that many weeks as one would expect the copy numbers of the virus to be in the hundreds of thousands during acute infection. If it was undetectable, then one would expect an excellent antibody response therefore your antibody test should have been positive or indeterminate.

The best suggestion that I can give you is to still follow up with an elisa at 12 weeks and completely put it to rest. The chances of BOTH tests, at the correct time frames, being falsely negative is pretty close to zero.

But as I always say....do your own research and decide on a testing strategy that you are comfortable with.

Best of luck.....

Tex



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Anonymous
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Re: Accuracy of PCR new
      #15265 - 01/30/01 10:17 PM

The human body antibodies for hiv are a poor "device" for keeping the hiv virmen "contained" (i.e. low viral loads are porbably based on the virus's virulence). The virulence is based on the hiv's strain/DNA nomenclature. Additionally,

"If HIV antibodies were strong enough to keep the viral load undetectable then we wouldn't need HIV therapy, since everyone with HIV has HIV antibodies, and most of them have detectable virus."
Dr. Joel E. Gallant, HIV antibodies vs. viral load, (hiv testing) 10 June 98.






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Anonymous
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Re: Accuracy of PCR new
      #15291 - 01/31/01 04:32 PM

Can you tell me what you know regarding the accuracy and timing issues associated with HIV PCR testing? I have been told that the minimum time frame is 28 days following the last possible exposure. Additionally, I've read a lot about a high level of false positives associated with this test (are there distinct statistics for this?). I realize that I need to follow up with a 3 and/or 6 month antibody test. For my own sanity, however, I feel I must move forward with the PCR testing.



Ryan Kull's Response:
PCR tests are not licensed as tools for diagnosing HIV infection, so there are currently no clear standards set for using PCR tests to detect infection. HIV PCR tests are only approved for monitoring viral load in infected persons. The p24 antigen test is the only licensed tool for detecting infection earlier than the antibody tests (it is used in screening blood donations), but is not as sensitive as PCR testing for viral RNA. The p24 test is more likely to be falsely negative than PCR testing or antibody testing after the window period because it lacks the other tests' sensitivity.

A recent review of literature on primary HIV infection states that PCR tests for viral RNA can detect infection one to three weeks earlier than the standard antibody test (which is about, on average, 3-4 weeks following infection). Virus has been detected in plasma anywhere from 4 to 11 days following infection. While false positives on viral-RNA tests are rare, they are more common than false positives on antibody testing because of the PCR's increased sensitivity and the technical complexity of performing the tests.


PCR tests are most meaningful when a physician is attempting to diagnose symptoms that suggest acute infection (when viral levels should be high). Otherwise, since levels of virus in an infected person are variable based on immune response, viral characteristics, and type of test used, a PCR test used alone is not sufficient. PCR testing should ALWAYS be confirmed with antibody testing after the window period has elapsed.


RMK





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Anonymous
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Re: Accuracy of PCR new
      #15307 - 01/31/01 09:42 PM

Question:
How can one be undetectable and still know they have the HIV virus? I am having a hard time understanding this concept.



Dr. Holodniy's Response:
When refer to "undetectable" in this forum, it is usually regarding the viral load test. That test measures HIV RNA in the blood plasma. In almost all HIV infected people, the viral load is detectable in the absence of treatment. It becomes undetectable with treatment. People will still have a positive antibody test and will have a positive DNA PCR test (measures HIV in blood cells).
MH








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Anonymous
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Give ME a break new
      #15310 - 02/01/01 12:45 AM

Do you know what he and the CDC are saying. They are saying that the ONLY way to confirm ANY test is an Elisa (antibody) taken after the window period! Meaning that any test you take (to include an elisa) needs to be confirmed with an elisa (antibody) at 6 months!

I think that the rates for false + would be no more than 5% (if that). Couple this with an antibody test at 3-months like the GMHC says (will be about 100%) -- so why wait for 6 months.



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TexGal
Master

Reged: 11/21/00
Posts: 139
Re: Give ME a break new
      #15320 - 02/01/01 12:28 PM

From the responses I read from Kull, he seems to be a big supporter of the 3 month Elisa. He has stated previously that he agrees with the GMHC and the NYS Dept of Health that a 3 month elisa is sufficient. And that's without a PCR test.

Even Dr. H has said that with the use of PCR testing, it is making the 6 month elisa follow up less necessary because of the negative predictive value of both tests combined.

If I'm wrong, let me know but I believe that is what I have read.

Tex






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