Background The direct oral anticoagulant (DOAC) dabigatran is a direct thrombin inhibitor. Its landmark trial, the RE-LY study, observed a trend towards a higher incidence of myocardial infarctions (MIs) in dabigatran-treated patients. Since then, there have been discussions on whether dabigatran increases the risk of MI. Objective In this study, we aimed to assess platelet reactivity and platelet thrombin receptor expression in dabigatran-treated patients. Methods We conducted a cross-sectional study in 13 hospitalized patients with planned initiation of dabigatran medication. Platelet reactivity was measured by light-transmission aggregometry and platelet thrombin receptor expression was measured by flow cytometry analysis. Results Platelet reactivity was higher after initiation of dabigatran medication as compared with baseline (baseline 44 ± 24% vs. dabigatran 70 ± 25%). Accordingly, the density of both platelet thrombin receptors (protease activated receptor [PAR]-1 and PAR-4) on platelets increased during dabigatran treatment (PAR1, baseline 63 ± 11% vs. dabigatran 70 ± 10%; PAR4, baseline 1.1 ± 0.5% vs. dabigatran 1.6 ± 0.9%). Conclusions Dabigatran increases platelet reactivity by enhancing the thrombin receptor density on platelets. This finding should be considered while choosing the optimal DOAC in individualized medicine.

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We describe the unique disease course and cure of SARS-CoV-2 infection in a patient with SCID and graft failure. In absence of a humoral immune response, viral clearance was only achieved after transfusion of convalescent plasma. This observation underscores the necessity of the humoral immune response for SARS-CoV-2 clearance.