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    Poster Networking

    Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies

    Poster Networking Session

    PB1338 - Thrombotic Thrombocytopenia Syndrome after vaccination against COVID-19 associated with antiplatelet antibodies.

    Tuesday, June 27, 2023
    18:30 – 19:30 ET
    Room: Exhibition

      Presenting Author(s)

    • Thomas Thiele, MD

      Head of Department
      Universitätsmedizin Rostock, Institut für Transfusionsmedizin
      Rostock, Mecklenburg-Vorpommern, Germany

      • Co-Author(s)

    • ME

      Max Esefeld

      Physician
      Universitätsmedizin Greifswald, Institut für Transfusionsmedizin
      Greifswald, Mecklenburg-Vorpommern, Germany

    • SH

      Stefan Handtke

      PhD
      Universitätsmedizin Rostock
      Rostock, Mecklenburg-Vorpommern, Germany

    • JR

      Justina Rath

      Student
      Universitätsmedizin Greifswald, Institut für Transfusionsmedizin
      Greifswald, Mecklenburg-Vorpommern, Germany

    • Linda Schönborn, Dr. med.

      Medical Resident
      Institut für Transfusionsmedizin, Universitätsmedizin Greifswald, Greifswald, Germany
      Greifswald, Mecklenburg-Vorpommern, Germany

    • JA

      Jovan Antovich

      Professor, Senior Consultant
      Karolinska University Hospital, Dept. Clinical Chemistry
      Stockholm, Stockholms Lan, Sweden

    • KL

      Kourosh Lotfi

      Physician
      Linköping University, Dept of Hematology
      Linköping, Ostergotlands Lan, Sweden

    • MH

      Margareta Holmström

      Consultant physician
      Linköping University Hospital, Dept. Acute Internal Medicine and Geriatrics
      Linköping, Ostergotlands Lan, Sweden

    • LH

      Lukas Harasser

      Physician
      Innsbruck, Universitätsklinik für Innere Medizin IV - Nephrologie
      Innsbruck, Tirol, Austria

    • CF

      Clemens Feistritzer

      Physician
      Universität Innsbruck, Klinik für Innere Medizin V, Hämatologie
      Innsbruck, Tirol, Austria

    • LL

      Lorin Loacker

      Physician
      Universität Insbruck, Dept. Clinical Chemistry
      Innsbruck, Tirol, Austria

    • TH

      Till Hoffmann

      Senior Consultant
      Universitätsklinikum Düsseldorf, Dept.Transfusionsmedizin
      Düsseldorf, Nordrhein-Westfalen, Germany

    • SW

      Saskia Wunderlich

      Physician
      Darmstädter Kinderkliniken Prinzessin Margaret
      Darmstadt, Hessen, Germany

    • Andreas Greinacher, MD

      Professor; Head of Institute
      Institut für Transfusionsmedizin, Universitätsmedizin Greifswald.
      Greifswald, Mecklenburg-Vorpommern, Germany

    Background: Thrombosis and Thrombocytopenia syndromes (TTS) can occur as adverse reactions following vaccination against SARS-CoV-2. The most prominent example of TTS is vaccine-induced immune thrombotic thrombocytopenia (VITT); being caused by IgG-antibodies directed against platelet factor 4 (PF4). However, other entities of antibody mediated TTS may exist apart from VITT.

    Aims: Description of laboratory and clinical features of patients with TTS testing negative for anti-PF4-IgG after vaccination against SARS-CoV-2.

    Methods: Sera of patients with TTS send to the Greifswald laboratory after SARS-CoV-2 vaccination were tested for anti-PF4 antibodies by ELISA and for antiplatelet antibodies by the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay. Anti-PF4-IgG negative sera testing positive for antiplatelet antibodies by MAIPA were further analysed for their ability to induce procoagulant platelet formation in healthy donor platelets by measuring phosphatidylserine (PS) exposure. Clinical features of patients were extracted from request documents.

    Results: We identified 18 patients with TTS in temporal relationship to SARS-CoV-2 vaccination (median onset: 16 days, range 1–60 days) who tested negative for anti-PF4 antibodies. All patients showed thrombocytopenia (86,000/µl, 2-127/µl); petechiae were documented in 5 patients. Venous thromboembolism was reported in 11 patients, arterial thrombosis in 5 patients, 1 showed disseminated intravascular coagulation and 1 developed clots in arterial and venous vessels. 7/18 sera tested positive for antiplatelet antibodies, including 2 with anti-GPIIb/IIIa, 1 with anti-GPIa/IIa, 1 with anti-GPIb/IX/V, 2 with anti-GPIIb/IIIa and anti-GPIb/IX/V; and 1 with anti-GPIIb/IIIa, anti-GPIa/IIa and anti-GPIb/IX/V antibodies. These sera strongly induced procoagulant platelet formation when incubated with fresh donor platelets. PS-exposure was blocked by inhibition of the Fc-gamma IIa receptor and GPIIb/IIIa.

    Conclusion(s): Antibody-mediated TTS can develop in presence of antiplatelet antibodies, which are able to induce procoagulant platelet formation via the Fc-gamma receptor. This entity of TTS is distinct from VITT and its relationship to vaccination needs further evaluation.