They do blood culture, and look for the bacteria itself, and use immunohisto staining so they can be sure it is borrelia
Serology Elisa and Western blot you can never be fully sure if past or present infection. With blood culture if postive it is positive, they have no false postive so far
Their method has been published in serious scientific medical journal also, not instead of ELISA but in addition
Advanced lab do blood culture for borrelia, galaxy lab for Bartonella ....u must be off Antibiotics at least 4 weeks before doing these test to have high chance of detection