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Avatar universal

what's up with PCR testing

Can anybody tell me is getting private clinical PCR testing safe and accurate?
I 'm thinking about getting tested at labcorp just to ease my mind.
75 Responses
Avatar universal
PCR testing is accurate if taken after 28 days from exposure. But remember it is a very sensitive test and can have chances of giving false positive result. Unless you are involved in a high risk exposure, doctors do not recommand taking this test because of its sensitivity and chances of giving false positive result. But once tested negative you don't have to worry anymore since it it checking for virus through DNA rather then blood which takes longer time to come in contact.
Avatar universal
A PCR test is not for the purpose of screening or diagnosing someone that believes they have contracted HIV. A PCR test is used to monitor the viral load of persons already infected with HIV to see how their medication is or is not working.
Avatar universal
2 reasons PCR testing is not recommended:

1) Possibility of a false positive result, which obviously, would freak you out, even though you do not have HIV.

2) It costs too much money.  Also it's a time-consuming test.  At 28 days, the possibility of testing positive on an antibody test is 90-95% if you are truly infected, so it just doesn't make sense to spend your money on the PCR test.

However, if you do test negative after 28 days, it is highly accurate, and if you want to spend the money to avoid feeling the anxiety, then go ahead and do it.
Avatar universal
The main reason they're not recommended are, they are not approved for diagnosing anyone that thinks they had a possible exposure. They are approved to test infants that were born to infected mothers just because most infants will test positive the first 15-18 months due to antibodies from the mother and all other test would come back possible positive and the PCR is used to help rule HIV out.
Avatar universal
Teak, you're right, that's what the CDC says about PCR testing.  But my comments are from Dr. HHH's words in one of the threads that I saw, and although I'm not his biggest supporter (b/c I think he's too liberal on his opinions sometimes), I do agree with his comment on the PCR testing.
Avatar universal
too liberal on his opinions?  more like too conservative when it comes to risk assessment.
I have been reading these "Archives" and it seems to me that he suggests heteros test out to 6-8 weeks and homos like myself test out to 3 mos.

Aren't all testing methods the same regardless of risk?
Is not a risk a risk?

Do tell.
219662 tn?1223862160
Look people, PCR is a FINE test for all purposes.
The bottom line is that ELISA is a BETTER test for multiple reasons (fewer false negatives, fewer false positives, cheaper, faster, etc. etc.).  Thus it is a recommended test, not PCR.  If you are 6 weeks or more post-exposure forget PCRs, take an ELISA and then move on, end of story.  
Avatar universal
Not all test methods are the same, but the testing guidelines for str8 or gay are the same. 3 months is when you can get your conclusive negative test no matter if your str8 or gay.
Avatar universal
well, I spoke to some person from GMHC today and they said that at 4 weeks 90-95% show up.
Tell me,..is this true?
Avatar universal
yes, that is true for most people, though some people take longer to develop antibodies
Avatar universal
well, if say 90% people show up at 4 weeks, then that leaves 10%
And of the 10%, that means you either got HIV or Not ?  5%
That means the test would indeed be 95% accurate if negative at 4 weeks...right?
The other 5% would have ot include an array of other factors,..such as entry way, the risk, etc..
Avatar universal
Read this from GMHC on testing. http://gmhc.org/health/testing.html
Avatar universal
I did...and I was not talking about PCR....but standard HIV antibody testing
Avatar universal
Only the last part talked about PCR. I was talking about the window period.
Avatar universal
yeah...I saw it. But the "vast majority" of people must be 90-95% of people...the "unvast majority" must be some seriously ill people.
Avatar universal
and as far as I know...i do not have cancer or inject drugs
Avatar universal
my concern was more on the performace of oral sex on a man who is gay and did not ejaculate in my mouth.
I just did not know if I had any oral cuts/abrasions that could have exposed me.
Avatar universal
For those that are on chemo, anti-rejection drugs or chronic drug abuse only amount to 3%.
Avatar universal
You didn't have a risk, so if you want to test the day after it would be conclusive.
188761 tn?1570897452
You have to understand that there are two types of PCR tests which looks for the HIV Proteins

Irrespective of the PCR type,the false positive rates have drastically dropped and every positive PCR is confirmed with another PCR for confirmatory reason, this eliminates the possibility of small amount of false positives(which was always 4%).

The HIV DNA PCR test measures something different than the HIV antibody. The DNA PCR test looks for HIV DNA in the white blood cells of a person, whereas the  ELISA (antibody tests) measure the immune response to the virus. If a person has a HIV DNA PCR test, the result may be positive even if insufficient antibodies are present for detection by the HIV antibody ELISA.An undectable PCR DNA taken at 28 days or more from the time of exposure only suggests no HIV infection.

The HIV RNA PCR test detects the HIV infected RNA directly. The time between HIV infection and RNA detection is 9-11 days.Hence, an undectable PCR RNA at 12 days or more from the time of exposure suggests no HIV infection.

Today, the advance PCR tests looks for as low as 10 copies of DNA/RNA in 1 ml of blood. If we analyze logically, after acquiring HIV the virus multiplies in great magnitudes every day and after 2 - 3 week post exposure, the viral count should be in thousand to millions, if an ultra sensitive PCR test with sensitivity of 10 -50 copies of DNA or RNA / ml of blood was undetected, you should be rest assured that you weren't infected at the first place.

It's always recomended to back up your undetectable PCR result with an antibody test at the 12 weeks. One can only expect a negative.

Good Luck

Mike :)
219662 tn?1223862160
OK, I don't mean to be anal, but I think I've seen you say this many times before, so here it goes:

PCR tests do NOT look for proteins.  They detect genetic material - DNA or RNA.
188761 tn?1570897452
Joey ...why do you do this ?

I've said another thing time and again that you can STFU, if you don't know, just don't make up :D (I'm not attacking on you here, I'm kinda feeling funny, joey will always crisscross mike )


Go figure out!
188761 tn?1570897452

My apologies, I take my words back again, I skipped my mind on Elisa and PCRs.


Pardon my Ignorance

219662 tn?1223862160
I rarely correct people here, because I believe that everyone is entitled to an opinion and because I know how much people hate to be corrected.  I do it only when someone is blatantly wrong, because I feel that I have that responsibility.  This was such a case and I knew that it wasn't simply a typo, because I've seen you say this before - and I only read maybe 5% of the threads here.  I won't make exceptions just because one is a regular poster, like yourself.  It does not give me any pleasure, I don't do this to crisscross anyone.  I wish somebody else would do this, but no one does, especially now that guiltworry and a few other competent people are no longer here.  

I accept your apology.  All I can say is that you shouldn't get so angry, it's OK to be wrong.  Arguing with regularjoey is a waste of time, since I'm always right.  Try not to be such a hothead and you won't have to apologize again.  Cheers.
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