Why RNA PCR test not diagnostic?

I know I can't shake this, but why again is the supersensitive RNA PCR test after a few weeks from exposure not diagnostic if negative?  I know the problem with this test is occasional false positives but are false NEGATIVES ever a concern especially if different subtype of HIV-1?  Is it possible to be both RNA PCR negative and ELISA negative after an 8 week test and still become positive after a high risk exposure?

[mike_no]

Ho Ho Ho, in that case it would be the best time to party....Lol

buddy, first things first
1. PCRs (NAT) are the most sensitive test, they're capable of detecting the virus right after 72 hours of the exposure

2. HIV virus replicates in MILLIONS every day

3. A PCR test if done on some body with HIV at 6-8 week the viral load reading would be SKY HIGH

4. Having said that all what I mean here is PCR at 6-8 week is 100% conclusive

[dobber21]

RNA has a higher risk of false positives. It's only really for use if the doctors believe someone is actually going through ARS, as it has been shown in certain studies that early treatment can halt disease progression.

As for you, is it possible for you to be positive after those tests? No it is not. Here's why.

if you'd been infected, the virus would be in your system. The typical host response is to create antibodies. These show up on a test anywhere from 2 weeks to 13 weeks in pretty much everyone. However, if your body was incapable of creating antibodies, the virus would replicate at such a level that your viral load would remain extremely high, and therefore detectable on an RNA.

Ergo, your negative. Official recommendations say test out to three months. This option is open to you. It will be negative:)

[scared83]

PCR tests produce an unusually high number of false positives. I shelled out $300 to get a PCR test, came home and read that there are way too many false positives so I never called back for my results. Waste of $300.00!! But a false negative almost never happens. If you have a false negative, then you are negative but you had to have taken the PCR test at the right time. Anywho, I'd suggest an atibody test because those are the industry standard, not PCR tests. And contrary to what the Lab Tech's who perform PCR tests will tell you, it is not the way to diagnos HIV.

Speak with an Infectious Disease Doc, he or she will tell you the same thing.

[scared83]

I mean to say, "If you have a negative PCR, then you are negative" NOT "if you have a false negative"

My mistake

[dobber21]

My response is open to comment; I'm not quite sure if I hit the nail on the head but I'm sure those that are far more knowledgeable than me will put me in my place if I'm not:)

[shiblee101]

one day hopefully when an hiv vaccine works to prevent infection, the only way to really tell infection will be pcr (the actual virus) because antibodies would normally be made to a vaccine.  ultimately, it would seem to me that RNA PCR is a better test (if not for the false positives) in ruling out infection especially since the newer tests are supersensitive down to reading 50 copies of the virus.  i'm no expert but am i theoretically right.  a good RNA PCR test could really bring down the window period (to a few weeks post exposure) and help with anxiety that goes along with hiv.

[mike_no]

Going by the CDC, A RNA PCR at 9-15 days is conclusive, I can't find the link but i'll post the same here ASAP once I find it

To avoid the possibility of false negative one can rely on a Real Time PCR RNA (SDS), it's ultra sensitive (more sensitive than RNA PCR)

Regards
Mike

[shiblee101]

BUT when the RNA PCR test comes back NEGATIVE after about 6-8 wks from exposure in addition to a negative ELISA, you can be fairly certain that you are not infected right?  This is not likely to change?

[mike_no]

the one you're talking about is real time PCR( SDS),SDS has the set benchmark of detecting above 50 copies/ml, it's just different terminologies people know them with

BTW check whether the Probe used is : taqman ?

any ways whether SDS or PCR RNA if yeilede a negative result, it's a reliable result for sure !

[Teak]

PCR RNA testing not unlike the ELISA test must be backed up with other antibody tests. Neither are stand alone tests, when the test has reacted positive.

[shiblee101]

what is the difference b/w real time rna pcr (sds) and supersensitive rna pcr (detecting up to 50 copies)?

[Teak]

The way the the PCR RNA test is approved in "aiding the diagnostics of HIV," I would have to say no, that a PCR test by itself is not a conclusive test. If it were, it would have been approved in that manner. I don't know the reason, the test was not approved as a stand alone test.

[mike_no]

I think that very well answers my question but I'm sure you'd agree to this, one can rest a bit easy after an 'undetectable' PCR result

[Teak]

Gen-Probe Receives FDA Approval for APTIMA(R) HIV-1 RNA Qualitative Assay for Clinical Diagnostic Use

PRNewswire - October 5, 2006


--------------------------------------------------------------------------------
-- New Product Will Be Launched in Conjunction With APTIMA HCV RNA Qualitative Assay
SAN DIEGO, Oct. 5 /PRNewswire-FirstCall/ -- Gen-Probe (Nasdaq: GPRO) announced today that the U.S. Food and Drug Administration (FDA) has granted marketing approval for the APTIMA(R) HIV-1 RNA qualitative assay. The assay may be used as an aid in the diagnosis of acute and primary HIV-1 infection, and to confirm HIV-1 infection in an individual whose specimen is repeatedly reactive (positive) for HIV-1 antibodies. The assay is the first FDA-approved qualitative nucleic acid test (NAT) for these intended uses.

PCR RNA is not a conclusive test. It is a AID in the diagnosis of acute primary HIV 1 infection.

[mike_no]

Hello Teak,

I completely undertand the point and also thank you for the news

But sombody who's got an 'undetectable' PCR result at the 6-8 week wouldn't you think it's conclusive

Regards

Mike