Seroprevalence and seroconversion of Lyme borreliosis among tick-bitten individuals: A multi-assay serosurveillance study

Lyme borreliosis (LB), caused by different species belonging to the Borrelia burgdorferi sensu lato group, is the most common tick-borne disease in Europe. However, its true burden remains difficult to assess, partly due to the diagnostic variability of commercial assays. This study evaluated seroprevalence and seroconversion following tick bite, using four serological assays with distinct antigenic compositions. Participants provided blood samples within three days of the tick bite and three months after to assess seroconversion. We evaluated the seroprevalence, seroconversion, inter-assay variation, consensus scoring, and factors affecting the detection rate for both seroprevalence and seroconversion. Seroprevalence evaluation varied across the four serology assays: 33% using Anti-Borrelia plus VlsE (ABV), 26% using Epitogen™ Lyme (Epitogen), 22% using C6 Lyme ELISA (C6) and 10% using IDEIA™ B. burgdorferi (IDEIA). Estimation of overall seroconversion rates also differed: C6 had the highest rate (93%), followed by Epitogen (78%), ABV (58%) and IDEIA (38%). Using a consensus scoring approach that required positivity of at least two assays (including immunoblot) yielded a seropositivity rate of 23% at inclusion and an overall seroconversion rate of 86%. The Epitogen assay showed the highest level of concordance with the consensus score, followed by C6, ABV, and IDEIA assays. Seroprevalence and seroconversion estimates in LB are highly assay-dependent. Assay choice significantly influenced outcome, mainly reflecting differences in antigen composition. This study underscores the importance of evaluating the antigen composition used in assays to ensure accurate result interpretation, particularly in the context of potential species variability across differing geographical regions. The use of consensus scoring across complementary multi-assays, or the implementation of well-designed assays with appropriate antigen coverage, offers a pathway to improved diagnostic accuracy and enhanced comparability.