Diagnosis of borreliosis depends on the appropriate diagnostic procedure: selection of the appropriate diagnostic methods, as well as the correct interpretation of the results and clinical signs.
According to the recommendation of the Polish Society of Epidemiologists, serological diagnosis is a two-step process. The diagnostic protocol includes the use of ELISA (enzyme-linked immunosorbent assay) screening tests to detect specific IgM or IgG antibodies and Western blot, to verify the results obtained by ELISA.
Specific antibodies against antigens of Borrelia burgdorferi s.l. may be detected in the serum, plasma or CSF (Cerebrospinal Fluid).

MONITORING OF THERAPY - EUROLINE (EUROIMMUN AG, Luebeck, Germany)
EUROLINE tests are used for the diagnosis of borreliosis as well as monitoring of the effectiveness of therapy. In these tests, specific antibodies against a highly immunogenic antigen (VIsE) are detected. VlsE (variable major protein-like sequence, expressed) is a surface protein of Borrelia burgdorferi which plays a key role in the survival strategy of Borrelia. A recombinant VIsE antigen is used as an early-stage disease marker (regardless of the species) which enables the identification of atypical reactions and ensures a high sensitivity.
Monitoring the effectiveness of treatment is a two-step process and is based on determining the antibody titer against VIsE just before treatment and 8-12 weeks after the end of antibiotic therapy.
In the case of an effective treatment, the level of anti-VIsE antibodies is rapidly lowered to below detectable levels, while other antibodies may still be detected by ELISA.