ODSH and UFH but not dabigatran or rivaroxaban prevent anti-PF4/heparinAb-induced platelet activation. Sera from patients containing anti-PF4/heparin IgG were tested in the HIPA with 0.2 IU/mL LMWH in the presence of increasing concentrations of UFH, ODSH, dabigatran, or rivaroxaban. In addition, ODSH was also tested in the presence of 0.2 IU/mL UFH. Fifteen (DMSO, n = 14) platelet donors were tested with 3 different patient sera for each anticoagulant. The figure shows the number of donors with platelet activation until 45 minutes. At a concentration of 1.04 μg/mL, ODSH started to inhibit platelet activation by anti-PF4/heparin Abs in the presence of LMWH (■), while lower concentrations of ODSH were needed in the presence of UFH (□). Dabigatran had almost no effect. The inhibition of platelet activation with high concentrations of rivaroxaban was because of its solvent carrier DMSO.