The authors tried to confirm data on the prevalence of antiborrelia antibodies class IgM and IgG in the local healthy population (200 blood donors) and in subjects with an increased risk of infection (forestry labourers, forestry workers and huntsmen). All blood samples were analyzed in the National Reference Laboratory for Lyme borreliosis CEM (LB) in the National Institute of Public Health in Prague by the ELISA NRLB KC 90 method and in case of a positive result they were confirmed by the Western blot Lyme method. All patients completed a special questionnaire used as a standard procedure in the consultation centre for LB. In the group of blood donors 100 men were examined, mean age 33.5 years and 100 women, mean age 24.4 years. In 26 positive antibodies against Borrelia burgdorferi (Bb) were confirmed, but on invitation to medical examination only 22 attended, 11 men and 11 women (10.1%). Examination of antiborrelia antibodies by the ELISA method proved positivity of class IgM 7 times and of class IgG 9 times. By the Western blot method (WB) class IgG was confirmed three times. In the risk group 39 men were examined, mean age 40.6 years and 32 women. In 12 of them (17.9%) positivity of antiborrelia antibodies against Borrelia burgdorferi (Bb) was proved by the ELISA method as well as the WB method. If the percentage confidence interval of the control group is taken as a basis for comparison, then the value of the risk group is within this interval at a significance value of alpha = 0.01. In the conclusion the authors discuss the problem of interpretation of positive serological results and the pitfalls of their evaluation not only from the aspect of validity of laboratory findings, due to the absence of standardization of methods, but also with regards to obscure aspects of the persistance of IgM antibodies after years of lege artis antibiotic treatment.

        Key words: Lyme borreliosis – prevalence – antiborrelia antibodies – ELISA Lyme – Western blot Lyme.