Determination Of Anti-Adamts-13 Autoantibody Titers In Elisa: Influence Of Adamts-13 Presentation And Autoantibody Detection

Background Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is caused by inhibitory and/or clearing anti-ADAMTS-13 (A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats, member 13) autoantibodies. To determine the presence and total level of anti-ADAMTS-13 autoantibodies, commercial and in-house developed ELISAs are performed. However, different ELISA methods vary in relation to the presentation of recombinant (r)ADAMTS-13 and the detection method of the anti-ADAMTS-13 autoantibodies. Currently, the influence of those different approaches on anti-ADAMTS-13 autoantibody titers is not known. Objectives To assess the influence of different ADAMTS-13 presentation- and autoantibody detection methods on anti-ADAMTS-13 autoantibody titers in ELISA. Materials/Methods Anti-ADAMTS-13 autoantibody titers from 18 iTTP patients were determined using four different set-ups of anti-ADAMTS-13 autoantibody ELISAs. The ELISAs varied in the used presentation of rADAMTS-13 (directly coated full-length rADAMTS-13, directly coated rMDTCS and rT2C2, or antibody-captured full-length rADAMTS-13) and the detection antibodies (polyclonal anti-human IgG or monoclonal anti-human IgG(1-4) antibodies). Results Strong correlations between the different anti-ADAMTS-13 autoantibody ELISA approaches were observed, when using polyclonal anti-human IgG detection antibodies recognizing all IgG subclasses similarly, independent of the method of rADAMTS-13 presentation. Anti-ADAMTS-13 autoantibody titers correlated less when using a mixture of monoclonal anti-human IgG(1-4), because not all IgG subclasses were recognized with similar affinities. Conclusion Anti-ADAMTS-13 autoantibody levels using different methods of rADAMTS-13 presentation strongly correlate. However, the levels of anti-ADAMTS-13 autoantibodies are highly dependent on the detection antibody used, which should detect all IgG subclasses (IgG(1-4)) equally well.