Posted on May 1, 2017 in Blog |
The following is an excerpt written by Dr. B. Robert Mozayeni from our book Lyme Savvy: Treatment Insights for Lyme Patients and Practitioners
Blood Test for Lyme
At the time of the tick bite and the rash, if someone has never been exposed to Borrelia before, they will not have antibodies to the Borrelia microbe.
It takes usually six to twelve weeks to see antibodies to Borrelia. These antibodies initially develop as Ig-M, within two to four weeks and then later as Ig-G within six to 12 weeks or more.
To evaluate a tick bite, the first test we do is the Western blot test. It should be done within a week or two before the exposure causes antibodies. This is to determine what the baseline antibody level was before the bite. It does not yet reflect antibodies produced as a result of a Borrelia exposure.
Typically, three months later one re-tests for Borrelia by the Western Blot to see if there has been a change in the antibody response between the initial and the 12-week post-bite test.
Bayesian Probability Decision Making
I want to make an important point here: Many clinicians and patients don’t understand it takes time (weeks) to produce antibodies.
I have seen many errors of diagnosis being made when the clinical history was classic for Lyme Disease and strongly diagnostic.
When you have a high probability of Lyme Disease before any testing, that probability cannot be altered by the result of a negative test because the prior probability was so high.
This is called Bayesian probability decision-making. It is the standard clinicians should use to make decisions. Lately, Bayesian adaptive clinical trials have become the leading edge method for conducting clinical research. It is all about probabilities. You have to know what your prior probability was before an event occurs in order to gauge whether or not that event really matters in your adjusted probability after an outcome is observed.
In the case of a clear-cut tick exposure, ECM rash and Borrelia, you can be certain you have Lyme and a negative test result should not change your mind.
In numerous consultations, I encountered physicians who had told their patient (who had a clear-cut positive Western blot test for Lyme) that because their clinical history didn’t match, they couldn’t possibly have Lyme Disease. I have also seen them look at a strongly positive result and say it can’t be right, it’s false, all because they don’t want to deal with the problem.
More testing information later . . . .