Ackermann-Gäumann et al.
Comparison of four commercial IgG-enzyme-linked immunosorbent assays for the detection of tick-borne encephalitis virus antibodies
Vector Borne Zoonotic Dis., 2019, in press, DOI: 10.1089/vbz.2018.2359
Since clinical symptoms of TBE are often unspecific, the diagnosis of TBE virus infection is done by laboratory analyses. Indirect immunofluorescence testing is rarely carried out. The neutralization assay is the most specific one but can only be performed in special laboratories. The method of choice is the enzyme-linked immunosorbent assay (ELISA) due to its simplicity, automatization, quick availability of test results and relatively low cost. The authors compared four commercial ELISAs: the Anti-TBE/FSME Virus IgG assay (Siemens, Marburg, Germany; assay 1), the Anti-FSME/TBE Virus ELISA (IgG) assay (Euroimmun, Lübeck, Germany; assay2), the Anti-FSME/TBE Virus ELISA „Vienna“ (IgG) (Euroimmun, Lübeck, Germany; assay 3) and the RI-DASCREEN FSME/TBE IgG EIA assay (R-Biopharm, Darmstadt, Germany; assay 4). A total of 9328 plasma samples have been screened by assay 1 and based on the results, 876 samples were chosen of which 348 were positive, 74 samples were equivocal, and 454 samples have yielded negative results in the screening test. Plasma samples were classified as a: from blood donors with TBE vaccination history, b: blood donors without TBE vaccination, but with vaccination against another flavivirus and c: blood donors with TBE and another flavivirus vaccination status.
Overall, qualitative test results significantly differed between the different assays. In total, discrepant results were observed for 326/876 samples (37.2%). With a proportion of 65.6% of samples yielding discrepant results, the degree of disagreement between the four assays was particularly high for sample group a. Assay 1 and 2 yielded a much higher proportion of negative results than assay 3 and assay 4, and the authors concluded that assay 1 and 2 may be less suitable for the detection of vaccine-derived antibodies than assay 3 and 4. Although cross-reactive antibodies to other flaviviruses will generate false-positive results in all ELISAs evaluated in this study, this problem seems to be more pronounced for assay 3 and 4.