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You can have a patient negative for the two tier test, but with a positive PCR for borrelia. As you know PCR has the greates specificity (there are many false negative) and the lowest sensitivity (there aren't flase positive at all). So I consider the two tiers test not 100% reliable. But, you see, I have Lyme, so I had to study that subject.
The CDC test for Lyme is a more conservative one (less sensitivity, more specificity †): if you test positive, then you have Lyme to a good degree of certainty. Such conservative testing is important in say research studies, where you want to make sure that all your cohort do indeed have Lyme disease.
Other Lyme tests can be more "speculative" (more sensitivity, less specificity †): if you test positive, you might well have Lyme, but there also is a good chance you may not. These more speculative tests might useful for patients who don't mind the possibility that a positive result may be wrong, and on testing positive will go ahead and try some of the Lyme treatments anyway, and see if they help or not. Which can be a good idea.
You can have a patient negative for the two tier test, but with a positive PCR for borrelia. As you know PCR has the greates specificity (there are many false negative) and the lowest sensitivity (there aren't flase positive at all). So I consider the two tiers test not 100% reliable. But, you see, I have Lyme, so I had to study that subject.
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