CXCL13 as a biomarker in the diagnostics of European lyme Neuroborreliosis - A prospective multicentre study in Austria.

Background: 'Definite Neuroborreliosis (NB)' is diagnosed with the presence of NB-specific symptoms, cerebrospinal fluid (CSF) pleocytosis and an elevated Borrelia Burgdorferi antibody index. However, some diagnostic uncertainties exist. The B-cell chemokine CXCL13 represents an emerging biomarker for the diagnosis and treatment of NB because its intrathecal concentration rises prior to the Borrelia antibody index and drops rapidly after antibiotic therapy. Nevertheless, due to lacking prospective data, a definite CXCL13 cut-off for the diagnosis of NB is still pending.

Objective: Definition of a CSF CXCL13 cut-off for the diagnosis of acute and untreated NB in a prospective study setting.

Design and methods: This multicentre prospective study involved 6 neurological departments treating patients in the Lower Austria district (1.7 million inhabitants). The controls were patients scheduled for a spinal tap but not clinically diagnosed with NB. Demographic data, clinical characteristics and blood counts, as well as inflammatory CSF values and CSF CXCL13-concentration were analysed.

Results: We recruited 440 adult patients, of whom 42 have been diagnosed as having an acute and untreated 'definite NB'. Three hundred ninety-eight patients were assigned to the control group. The median intrathecal CXCL13 concentration was 2384 pg/ml for patients with NB and 0 pg/ml for controls. The difference was highly statistically significant (P ≤ .001). A CSF CXCL13 cut-off of 271 pg/ml resulted in a sensitivity of 95.2% and a specificity of 97.2% for the confirmation or exclusion of NB.

Conclusion: Based on our results, we propose a CSF CXCL13 cut-off of 271 pg/ml with Euroimmun-Elisa for the diagnosis of acute and untreated NB. Due to its high sensitivity and specificity, CXCL13 is a strong candidate biomarker for routine NB assessment, especially in clinically unclear cases.