The biological diagnosis of Borrelia burgdorferi sensu lato infection is usually made by antibody detection in patient sera. Thus, serological testing (Elisa, immunoblotting) is essential for a biological diagnosis. Specific antibody detection is usually done in serum and CSF of patients suspected of
Lyme borreliosis. Laboratories must follow European recommendations to validate these assays in routine practice. Antibody detection lacks sensitivity in the early cutaneous phase of the infection. Therefore, serological testing is not recommended for the diagnosis of erythema migrans. The interpretation of serology must take into account the variability of Elisa sensitivity and specificity and the lack of standardization for Western-blotting in Europe. Besides these indirect diagnosis techniques, there is also direct detection of spirochetes by culture or by in vitro DNA amplification but these require adequate samples. These molecular tests must not be performed routinely, but only for specific clinical situations and in specialized laboratories only.