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. 2015 Jul;22(7):823-7.
doi: 10.1128/CVI.00026-15. Epub 2015 May 20.

Study of a Cohort of 1,886 Persons To Determine Changes in Antibody Reactivity to Borrelia Burgdorferi 3 Months After a Tick Bite

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Study of a Cohort of 1,886 Persons To Determine Changes in Antibody Reactivity to Borrelia Burgdorferi 3 Months After a Tick Bite

Ram B Dessau et al. Clin Vaccine Immunol. .
Free PMC article

Abstract

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 3 months after a tick bite are measured using enzyme-linked immunosorbent assays (ELISAs). One assay is based on native purified flagellum 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 3 months later from 1,886 persons in Sweden and the Åland Islands, Finland. The seroconversion or relative change is defined by dividing the measurement units from the second sample by those from the first sample. The threshold for the minimum level of significant change was defined at the 2.5% level to represent the random error level. The thresholds were a 2.7-fold rise for the flagellar IgG assay and a 1.8-fold rise for the C6 assay. Of 1,886 persons, 102/101 (5.4%) had a significant rise in antibody reactivity in the flagellar assay or the C6 assay. Among 40 cases with a diagnosis of Lyme borreliosis, the sensitivities corresponding to a rise in antibodies were 33% and 50% for the flagellar antigen and the C6 antigen, respectively. Graphical methods to display the antibody response and to choose thresholds for a rise in relative antibody reactivity are shown and discussed. In conclusion, 5.4% of people with tick bites showed a rise in Borrelia-specific antibodies above the 2.5% threshold in either ELISA but only 40 (2.1%) developed clinical Lyme borreliosis.

Figures

FIG 1
FIG 1
Histograms of the distribution of units of the first sample (ln, natural logarithm). (A) The flagellar IgG assay. (B) The C6 assay. The cutoff values are indicated by vertical broken lines. The cutoff value for the flagellar assay is equal to the calibrator value; thus, ln (1.1) = 0.1. For the C6 assay, the calibrator has a very low value, and the diagnostic cutoff value is at a higher level as a consequence of adding a fixed value of 0.3. The resulting value is around 1.4 on the logarithmic scale.
FIG 2
FIG 2
Results determined for the first sample collected when the tick was detected and for the second collected 3 months later for the flagellar IgG (A) and C6 (B) assays. The optical density reading of each sample was divided by the cutoff value. To indicate a statistically significant rise in seroreactivity, the values above 95% of the RC in seroreactivity are indicated with colored circles. Data from patients diagnosed with EM or other manifestations of LB are shown with larger solid points. All very low measurements below 0.1 and 1.5 for the second sample for the flagellar IgG and C6 assays, respectively, are recorded as representing no change. The scales are logarithmically transformed (base ln).
FIG 3
FIG 3
The RC over 3 months in seroreactivity for the flagellar IgG and C6 assays plotted to show coreactivity. A total of 40 patients with LB and 1,518 tick-bitten cases of patients without LB are plotted. Data from 328 non-LB cases with very low absolute measurements below 0.1 and 1.5 in the second sample for the flagellar IgG and C6 assays, respectively, have been removed.
FIG 4
FIG 4
ROC curve of data from the 40 cases of patients with LB compared to people with tick bites without LB as controls. For the RC determinations, the data from the 331 cases of patients with very low values have been removed. The C6 curve based on RC is shown with 95% bootstrapped confidence intervals. The sensitivities and specificities corresponding to RC thresholds of 2.7 for the flagellar IgG assay and 1.8 for the C6 assays are shown as black and red dots, respectively. The second serum samples alone have a low discriminatory power.

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