title: Relevance of the antibody index to diagnose Lyme neuroborreliosis among seropositive patients.
abstract: BACKGROUND
  No consensual criteria exist to diagnose neuroborreliosis. The intrathecal anti-Borrelia antibody index (AI) is a necessary criterion to diagnose neuroborreliosis in Europe, but not in the United States. Previous studies to determine the diagnostic value of the AI found a sensitivity ranging from 55% to 80%. However, these studies included only typical clinical cases of meningitis or meningoradiculitis, and none had a control group with CSF anti-Borrelia antibodies.
  
  
  METHODS
  We studied a sample of 123 consecutive patients with clinical signs of neurologic involvement and CSF anti-Borrelia antibodies. We determined the AI for all patients and a final diagnosis was made. Patients were then divided into three groups (neuroborreliosis, possible neuroborreliosis, control).
  
  
  RESULTS
  Thirty of the 40 patients with neuroborreliosis had a positive AI (AI sensitivity = 75%). Two of the 74 patients with another neurologic diagnosis had a positive AI (AI specificity = 97%).
  
  
  CONCLUSIONS
  The antibody index has a very good specificity but only moderate sensitivity. Given the lack of consensual criteria for neuroborreliosis and the absence of a "gold standard" diagnostic test, we propose pragmatic diagnostic criteria for neuroborreliosis, namely the presence of four of the following five items: no past history of neuroborreliosis, positive CSF ELISA serology, positive anti-Borrelia antibody index, favorable outcome after specific antibiotic treatment, and no differential diagnosis. These new criteria will need to be tested in a larger, prospective cohort.
authors.affiliation: Department of Neurology, University Hospital of Strasbourg, Louis Pasteur University, Strasbourg, France. blanc.frdrc@free.fr
authors.forename: F
authors.initials: F
authors.lastname: Blanc
authors.forename: B
authors.initials: B
authors.lastname: Jaulhac
authors.forename: M
authors.initials: M
authors.lastname: Fleury
authors.forename: J
authors.initials: J
authors.lastname: de Seze
authors.forename: S J
authors.initials: SJ
authors.lastname: de Martino
authors.forename: V
authors.initials: V
authors.lastname: Remy
authors.forename: G
authors.initials: G
authors.lastname: Blaison
authors.forename: Y
authors.initials: Y
authors.lastname: Hansmann
authors.forename: D
authors.initials: D
authors.lastname: Christmann
authors.forename: C
authors.initials: C
authors.lastname: Tranchant
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood / Q000134:cerebrospinal fluid*; D025065:Borrelia burgdorferi / Q000276:immunology*; D006801:Humans; D020852:Lyme Neuroborreliosis / Q000134:cerebrospinal fluid* / Q000175:diagnosis* / Q000382:microbiology; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000592:standards