This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background. Episodes of Lyme disease with erythema migrans (EM) may lead to prolonged seropositivity, making the use of serology to diagnose reinfection potentially problematic. The C6 antibody test is currently used in serologic diagnosis of Lyme borreliosis as a first tier assay. Methods. The charts of adult patients with EM who were enrolled in prospective studies at New York Medical College were evaluated to find patients for whom we had clinically diagnosed 2 episodes of EM. Anti C6 antibody index was determined on acute and convalescent (all but 1 collected within 42 days of the acute specimen) serum samples stored at 70 C, using the C6 ELISA test from Immunetics, Inc. (Cambridge, MA). If any specimen was reactive, the serum antibody was titrated in duplicate and a geometric mean titer calculated. Results. Of 29 patients identified with 2 episodes of EM, the 16 who were known to have had exactly 2 episodes and for whom adequate serum samples were available were studied. For 4 patients the time interval between EM episodes was ~ 1 year, and 3 patients each had a time interval of 2 yrs, 3 yrs, 4 yrs, and 5 years, respectively. 1st EM 2nd EM Acute + 15 (94%) 13 (81%) Conv + 16 (100%) 15 (94%) 4-fold rise in titer 5 (31%) 7 (44%) Conclusion. Although C6 testing was highly sensitive in 2nd episode EM, whether this represents new seroreactivity could not be determined. A 4-fold increase in titer between acute/conv samples occurred in 50% of cases. Serologic diagnosis of reinfection remains problematic.
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