A prospective study on the role of CXCL13 in Lyme neuroborreliosis

The definite diagnosis of acute Lyme neuroborreliosis (LNB) requires detection of an increased Borrelia burgdorferi-specific antibody index (AI). The B burgdorferi AI, however, is negative in up to 20% of patients with early LNB and can remain elevated for years after adequate therapy; both of these factors can make the diagnosis difficult. Recent retrospective studies suggested the chemokine CXCL13 as a potential biomarker for LNB. To evaluate its diagnostic value, we conducted a prospective study. From March 2008 to August 2009, CSF and serum samples from all patients in whom a B burgdorferi-specific AI was requested (n=692) and CSF analysis revealed CSF pleocytosis (n=192) were included in the study. Because of the low number of patients with untreated LNB, 13 additional retrospectively selected samples of patients with untreated LNB were added. CXCL13 concentrations were measured by ELISA and receiver operating characteristic curves were generated. CSF CXCL13 was highly elevated in all patients with untreated acute LNB (mean=15,149 pg/mL) compared with that in the patients without LNB (mean=247 pg/mL). At a cutoff of 1,229 pg/mL, the sensitivity of CXCL13 was 94.1%, which is higher than the AI (85.7%). Only 7 patients (5 with a CNS lymphoma and 2 with bacterial meningitis) had a CXCL13 level above the cutoff, resulting in a specificity equal to the AI of 96.1%. CXCL13 shows high sensitivity and specificity for acute, untreated LNB. This novel marker appears to be helpful in clinically atypical cases and, in particular, in early stages of the disease when the B burgdorferi AI is (still) negative.