title: Occurrence of antibodies to Borrelia burgdorferi in patients with nonspirochetal subacute bacterial endocarditis.
abstract: OBJECTIVE
  To determine the prevalence and specificity of antibodies to Borrelia burgdorferi in patients with nonspirochetal subacute bacterial endocarditis and assess whether increased levels of antibodies to B. burgdorferi were attributable to rheumatoid factor.
  
  
  METHODS
  Retrospective case-control study.
  
  
  METHODS
  Urban referral center in an area devoid of infected ticks as a source of endocarditis sera.
  
  
  METHODS
  Sera from 30 consecutive patients with culture-proven subacute endocarditis between 1979 and 1981 were compared with 30 control sera collected between 1989 and 1990. In addition, sera from 20 consecutive patients with rheumatoid arthritis who were positive for rheumatoid factor were collected between 1991 and 1992. Sera were compared with a convenience sample from 15 patients who met the criteria for Lyme disease.
  
  
  METHODS
  Antibodies to B. burgdorferi were assessed by enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis. IgM rheumatoid factor was quantified using solid-phase radioimmunoassay or latex agglutination techniques.
  
  
  RESULTS
  Thirteen of 30 patients with endocarditis (43%) compared with 3 of 30 normal controls (10%) had increased levels of antibodies to B. burgdorferi (P < 0.01). Of these 13 patients, only 1 had an immunoblot consistent with previous infection. The others had nonspecific immunoblots: 5 showed isolated 60-kd reactivity; 1 patient had isolated 41-kd reactivity; and 6 had no bands of reactivity. Immunoblots of the 3 controls with increased antibodies showed only isolated 41-kd reactivity. Thus, the specificity of the B. burgdorferi antibody test in patients with endocarditis was only 60% (95% CI, 42% to 78%), compared with 90% (CI, 79% to 100%) in controls. No correlation was noted between IgM rheumatoid factor and antibodies to B. burgdorferi in patients with endocarditis (r = 0.2; P > 0.2). Only 1 of 20 patients with rheumatoid arthritis without known bacterial infections had antibodies to B. burgdorferi.
  
  
  CONCLUSIONS
  Although a positive ELISA test for B. burgdorferi may be a "true positive," a positive serologic test alone does not ensure that the clinical problem is due to Lyme borreliosis. Cross-reactive antibodies to shared epitopes between B. burgdorferi and the endocarditis organism may account for the high false-positive results.
authors.affiliation: State University of New York at Stony Brook.
authors.forename: A T
authors.initials: AT
authors.lastname: Kaell
authors.forename: P R
authors.initials: PR
authors.lastname: Redecha
authors.forename: K B
authors.initials: KB
authors.lastname: Elkon
authors.forename: M G
authors.initials: MG
authors.lastname: Golightly
authors.forename: P E
authors.initials: PE
authors.lastname: Schulman
authors.forename: R J
authors.initials: RJ
authors.lastname: Dattwyler
authors.forename: D L
authors.initials: DL
authors.lastname: Kaell
authors.forename: R D
authors.initials: RD
authors.lastname: Inman
authors.forename: C L
authors.initials: CL
authors.lastname: Christian
authors.forename: D J
authors.initials: DJ
authors.lastname: Volkman
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D015748:Borrelia burgdorferi Group / Q000276:immunology*; D003429:Cross Reactions; D003951:Diagnostic Errors; D004697:Endocarditis, Bacterial / Q000276:immunology* / Q000382:microbiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D006801:Humans; D008193:Lyme Disease / Q000175:diagnosis; D012189:Retrospective Studies; D012217:Rheumatoid Factor / Q000097:blood
chemical_list: D000907:Antibodies, Bacterial; D012217:Rheumatoid Factor