This is topic Why is this PCR test not used for Diagnosing in forum Medical Questions at LymeNet Flash.

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Posted by losferwrds (Member # 19741) on :
There must be some shortfall or reason,

I don't have any faith in antibody testing and clinical diagnosis, I want proof

I read in cure unknown about a guy who they thought had ALS got diagnosed with this test.

1. You take antibiotics for 4 weeks, this will kill lyme spiroketes if you have them

2. You take urine samples over that time, see as the bugs die, they have to be excreted thru urine

3. You do a PCR test, thats is a test than looks for the bugs DNA in the urine.

4. If you find bugs DNA in your urine, you have it, no ifs ands or buts, you found dead bugs, and you know you have lyme.

Seems so simple and definative, why would it not be used with seronegative people for verification?

I understand alot of people are fine with clinical diagnosis', but for me the idea of taking 3 years of abx based on sysptoms, would be like a doctor putting me on chemo without showing me a cancer tumor.
Posted by tcw (Member # 15698) on :
PCR just has a high false negative rate for Bb. The bacteria just does not seem to be found reliably in common fluids (serum, CSF, synovial fluid, urine).

That does not mean that it will not work for you, but for many patients it does not find DNA to amplify.

Really, there is only true proof - positive culture confirmed by sequencing, but that is not practical for mainstream testing. If you want positive confirmation, PCR is likely the best you will get.
Posted by cactus (Member # 7347) on :
It is not used for verification because of false negatives.

I am one of the few who was definitely diagnosed by PCR. Seronegative (by CDC standards), but PCR positive.

According to Dr B, a positive PCR is very significant. But a negative one - it doesn't mean much.

Think of throwing a bucket of ping pong balls into a pool, and then dipping out some samples of pool water with another bucket.

Will your sample contain a ping pong ball? Maybe. More likely not.

If not, does that mean there are no ping pong balls in the pool? No - only that your sample did not contain any.

But you're right - having that proof positive is a helpful tool in choosing to continue to treatment.
Posted by duke77 (Member # 5051) on :
I think the test you are referring to is called the LUAT. I think it is over 4 days not 4 weeks. I had a positive LUAT and PCR, but a negative WB. Like House said dipping a cup in the ocean and filling it up, but not finding a fish in the cup, does this mean there are no fish in the ocean?
Posted by SForsgren (Member # 7686) on :
It is only positive 6-15% of the time. So, it is rarely worth doing. If positive, it's a good thing to have, but rarely happens.

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