Evaluation of IgG/IgM Immunoblots EUROLine to confirm Lyme Borreliosis

1. SSM2010 Evaluation of IgG/IgM Immunoblots EUROLine to confirm Lyme Borreliosis R. Lienhard1, M. Herzig1, A.-F. Constantin2 and O. Péter2* 1ADMED Microbiologie, La Chaux-de-Fonds et *2ICHV Microbiologie, Sion Purpose Diagnosis of Lyme borreliosis is mainly based on clinical features and serological tests. The two-tier strategy consisting of screening tests followed by a confirmation test is recommended by EUCALB. We evaluated new rapid IgG and IgM immunoblot assays for serological confirmation of Lyme borreliosis. Sera were evaluated by each laboratory with their own sera according to the kit instructions. Any discrepant result on a serum was retested in the second laboratory for final interpretation. Blot interpretation. EUROline (Euroimmun) immunoblots include 3 control bands (poly-Ig, IgM and IgG). The EUROlineScan software was used to evaluate the results. IgG interpretation criteria are based on VlsE bands as presented here: Fig1 : Bands presentation Material and Methods Patients’ sera (n=103) have been selected from the serotheque of our 2 laboratories in order to test the main Lyme disease’s stadium: early localized, early disseminated and late borreliosis. The selection included 56 erythema migrans (EM), 6 lymphocytoma (LCB), 19 neuroborreliosis (NB) with specific intrathecal antibody production, 10 Lyme arthritis (ARTH) and 12 acrodermatitis chronica atrophicans (ACA). All sera were clinically and serologically defined cases. Blood donors were selected from the endemic region of Neuchâtel to measure the seroprevalence. Fifty sera in IgM and 60 in IgG were examined. Results were compared with our home-made Western blots (hmWB) including various genospecies as B. burgdorferi sensu stricto, B. garinii, B. afzelii and B.valaisiana. Results Erythema migrans IgG Euroimmun Sensitivity = 51.8 % Western blot Sensitivity = 26.8 % Kappa ratio = 0.30 Neuroborreliosis IgM Euroimmun Sensitivity = 52.6 % Western blot Sensitivity = 68.4 % Tab 1 : Results obtained with EUROLine blot tests and the reference laboratories Western blots on sera of defined clinical symptoms Kappa ratio = 0.25 Discussion Blood Donors IgM The EUROLine IgG immunoblots shows 100% sensitivity in detecting late borreliosis as expected for ACA and ARTH. For EM, EUROLine shows better results for IgG with high sensitivity unusual for confirmation tests at this early stage of the disease. This is due to the importance of the VlsE antigen in the interpretation algorithm. EUROLine IgM yields lower sensitivity which gives a final IgM-IgG sensitivity of 67.8 % equal to the hmWB. For NB the sensitivity of EUROLine IgM (52.6%) vs hmWB (68.4%) lowers the good IgG results obtained. In this clinical situation, IgM test does not add much to the confirmation capability obtained with IgG blots. It is however of upmost importance to remind that intrathecal specific antibody test must be applied for neuroborreliosis diagnosis as immunoblots cannot confirm all the cases. EUROLine IgG seroprevalence (8.3%) was equal to hmWB (6.7%) however a higher number of sera gave undetermined results with EUROLine (13.3%) vs hmWB (3.3%). Once again IgM parameter shows lower specificity with prevalence of 10% vs hmWB (2% ), this is known for OspC and VlsE IgM reactions. Globally on IgM-IgG EUROLine gave less negative results on blood donor sera with specificity of 64.3% versus 88% with hmWB Euroimmun Sensitivity = 51.8 % Western blot Sensitivity = 26.8 % Kappa ratio = 0.31 Conclusion The high sensitivity and good results obtained with EUROLine IgG blots is mainly due to the known high sensitivity and specificity of the VlsE Bb antigen. IgM results gave lower satisfaction. The interpretation software gives a convenient report easy to use with a conventional scanner. Seroprevalence in blood donors is an interesting parameter allowing to interpret results with caution.