The problem with the current tests on antibodies for Borrelia & Co is that a negative result can mean that there is no infection with Borrelia, but also can it mean that your immune system is incapable of producing enough antibodies to show up on the test.
In a discussion with an expert specialist for Lyme disease it has become clear to me that there exist a simple blood test to determine if someone's body is capable of producing antibodies in general.
This is a very common thing and can be done in a regular blood check along with the test for Borrelia antibodies, like ELISA or Western Blot. Same blood test, but now with more information.
When it appears that the production of antibodies in general is normal and there are no Borrelia & Co antibodies, there is a small chance that infection has taken place. But when this general production of antibodies is below normal, then it is logical that specific Borrelia antibodies will not show up on the test, even when a definite infection with Borrelia is taking place.
By measuring both items (general and Borrelia antibodies) a better conclusion can be drawn from the blood test.
When it appears that the body produces too few antibodies in general, it must be clear that the tests based on antibody detection are not suited for this person.
Then the preference must go towards other tests like PCR where a search for Borrelia DNA is done or the LTT test where the reactivity of lymphocytes is an indication for the presence or absence of an infection.