Serological description of Estonian patients with Lyme disease, a comparison with control sera from endemic and non-endemic areas

Serological tests for Lyme disease are mostly not well standardized and cases of misinterpretation of test results by clinicians are rather common. The diagnostic value of serologic tests may also depend on the seroepidemiological situation of the population. The aim of the study was to compare the immunoblot pattern of Lyme borreliosis patients and control sera from endemic and non-endemic regions and to identify the most suitable interpretation criteria for our immunoblot test. Serum samples of 24 Estonian patients with Lyme disease, 12 sera from patients with tick-borne encephalitis, 40 Estonian control sera, and sera from 50 Laplanders from North Sweden where people usually never come into contact with ticks were tested for IgG antibodies to Borrelia. Sonicated lysate of Borrelia afzelii (strain ACA1) was used in immunoblot as source of antigens. In our test system the following interpretation criteria gave the specificity of 96% for Estonian population: greater than or equal to 1 band from p58, p21, p17 and p14 plus greater than or equal to 2 bands from p83/100, p39, p34, p30 and p25; or greater than or equal to 4 bands from p83/100, p39, p34, p30 and p25. The comparison of Estonian controls with Laplanders showed that subclinical infections with Borrelia are rather common in Estonia. Also the rate of other infections, giving rise to cross-reactive antibodies, may be more frequent in Estonians. The frequent reactions with Borrelia antigens in a healthy population complicate the serodiagnosis of Lyme disease.