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By R. B. Dessau et al.
Lyme borreliosis is a tick-borne disease caused by the bacterium Borrelia burgdorferi. The most frequent clinical manifestation is a rash called erythema migrans. Changes in antibody reactivity to B. burgdorferi three months after a tick bite are measured using ELISA assays.
One assay is based on native purified flagella-antigen (IgG) and the other assay is based on a recombinant antigen called C6 (IgG or IgM). Paired samples were taken at the time of a tick bite and three months later from 1,886 persons in Sweden and the Åland Islands. The seroconversion or relative change is defined as the measurement units from the second sample divided by the first sample. Thresholds for the minimum level of significant change were defined as the 2.5% percentile to represent the random error level. The thresholds were 2.7 fold rises for the flagella IgG and 1.8 fold rises for the C6 assays.
102/101 (5.4%) of 1,886 persons had a significant rise in antibody reactivity in the flagella or C6 assay. Among 40 cases with a diagnosis of Lyme borreliosis the sensitivity of a rise in antibodies was 33% and 50% to the flagella antigen and the C6 antigen respectively. Graphical methods to display the antibody response and methods to choose thresholds for a rise in relative antibody reactivity are shown and discussed.
In conclusion, 5.4% of people with tick bites developed a rise in borrelia-specific antibodies above the 2.5% percentile in either ELISA assay, but only 40 (2.1%) developed clinical Lyme borreliosis.
Source: Dessau RB, Fryland L, Wilhelmsson P, Ekerfelt C, Nyman D, Forsberg P, Lindgren PE. Changes in antibody reactivity to Borrelia burgdorferi three months after a tick bite. A cohort of 1,886 persons. Clinical and Vaccine Immunology, pii: CVI.00026-15. Online first, 2015 May 20. http://doi.org/10.1128/CVI.00026-15