R. LIENHARD¹, L. VON ALLMEN², L. BERTAIOLA-MONNERAT³, A. DUMOULIN⁴, M.L. TRITTEN¹, H.H. SIEGRIST<sup>1

1</sup>ADMED Microbiology, and Laboratory, National Reference Centre for Tick-borne Diseases (NRZK), La Chaus-de-Fonds, Switzerland, ²ADMED Microbiology, La Chaux-de-Fonds, Switzerland, ³Laboratory of Microbiology, Hôpital Cantonal, Fribourg, Switzerland. , ⁴Institut Central des Hôpitaux, Hôpital du Valais, Sion, Switzerland

Purpose. Cytokine CXCL13 was quantified in CSF to evaluate its diagnostic potential for neuroborreliosis. Material and Method. One hundred and sixty-two CSF samples were quantified for cytokine CXCL13 on the CXCL 13 ELISA (Euroimmun, Lübeck, Germany). A selection of 55 patients presenting neuroborreliosis with production of specific intrathecal antibodies (SIA) was used to test sensitivity. The determination of SIA in IgG and IgM was made using the IDEIA Lyme Neuroborreliosis test (Oxoid, Basel Switzerland). Specificity was tested on 77 CSF samples of patients presenting central nervous system disorder with known aetiology. A further 30 CSF samples coming from suspected neuroborreliosis with a negative SIA on our test, but a positive SIA determined in the primary laboratory were analysed. The recently defined cut-off value of 250 pg/ml was used. Results and Discussion. We obtained a sensitivity for CXCL13 of 85.5% and a specificity of 94.8%. In the group with suspected neuroborreliosis, 10 (33.3%) CSF were positive. CXCL13 chemokine secretion is not stimulated by any specific Borrelia burgdorferi s.l. antigen. This unspecific marker showed, however, a very highly specific answer for acute neuroborreliosis. Furthermore most unspecific reactions can be easily identified. Sensitivity was rather low, it showed a better correlation with IgM SIA than IgG SIA. A delay of antibiotic therapy is essential to consider testing CXCL13 as its level drops quickly after the first dose. This frequently unavailable information might be a reason for lower sensitivity. Conclusion. Quantitative CXCL13 in CSF should be implemented in neuroborreliosis diagnosis as SIA determination harbours some pitfalls and PCR sensitivity is not satisfactory.