[Lyme Borreliosis: Serological and Microbiological Diagnostics and Differential Diagnosis]

Lyme borreliosis caused by at least six Borrelia burgdorferi species, is the most important tick-borne disease in the northern hemisphere. With a wide spectrum of possible symptoms, the microbiological diagnosis of this disease is associated with a wide variety of ideas, divergent approaches and much uncertainty. The aim of the article is to introduce the treating physicians to a meaningful microbiological diagnostic procedure. Most important messages include that (I) the suspected diagnosis of Lyme borreliosis is first based on anamnestic data and clinical symptoms (compare "case definitions") which is substantiated by microbiological examinations; (II) microbiological diagnostics - primarily antibody detection, downstream PCR and culture - are only indicated if there are indicative symptoms, with typical erythema migrans not requiring microbiological diagnostics; (III) keep in mind: The more unspecific the symptoms are the lower the positive and the higher the negative predictive value of microbiological testing; (IV) serological diagnosis should follow a two-step procedure: a sensitive ELISA as first step, if reactive followed by immunoblot (IgM and IgG). Detection rates are ca. 50 % in localized, 70- > 90 % in disseminated early and nearly 100 % (only IgG relevant) in late disease; (V) in the immunoblot early forms of disease show a narrow band spectrum, late forms show a broad spectrum; (VI) methods that are not recommended for diagnostic purposes include lymphocyte activation or transformation tests (LTT, MELISA, ELISPOT), PCR or antigen detection from urine or blood, lymphocyte subpopulations, or direct detection of borreliae from patient material using dark field- or focus floating microscopy.