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Bleeding tendency in thrombocytopenic patients due to impaired defects in primary and secondary hemostasis

1Amsterdam UMC, Amsterdam, Noord-Holland, Netherlands, 2Medical University of Warsaw, Warsaw, Mazowieckie, Poland, 3Laboratory of Experimental Clinical Chemistry, Amsterdam UMC, Amsterdam, Noord-Holland, Netherlands, 4Department of Hematology, Oncology and Internal Medicine, Medical University of Warsaw, Warsaw, Poland, Warsaw, Mazowieckie, Poland, 5University of Amsterdam, Amsterdam, Noord-Holland, Netherlands, 6Laboratory of Experimental Clinical Chemistry, Vesicle Observation Center, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands, Amsterdam, Noord-Holland, Netherlands

Abstract Number: PB0331

Meeting: ISTH 2022 Congress

Theme: Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies » Inherited Thrombocytopenias

Background: It is unknown why a bleeding tendency occurs at or below a critical platelet concentration of 50 million platelets/mL.

Aims: We hypothesize that below this critical platelet concentration, not only primary hemostasis is inhibited by reduced platelet-platelet interaction, but also secondary hemostasis by an inhibited release of platelet-derived extracellular vesicles (PEVs).

Methods: Citrate-anticoagulated blood was collected from immune thrombocytopenia (ITP) patients (n=10) and healthy individuals (n=4) to study aggregation by Multiplate and PEV release in blood plasma (not stirred) by calibrated flow cytometry (Apogee A60-Micro, scatter triggering, EV diameter ≥160 nm). In all experiments, platelets were activated by 30 µM thrombin-receptor activating peptide (TRAP), and saline was used as a control. The Mann-Whitney U test was used to test for significant differences.

Results: Addition of TRAP to undiluted blood of healthy individuals induced aggregation (p=0.029) and increased the PEV concentration in 2 out of 4 individuals. In contrast, no aggregation and no PEV release were observed in blood from ITP patients (Figure 1).

Conclusion(s): Below a critical platelet concentration, activated platelets neither aggregate nor release PEVs. Thus, the bleeding tendency of ITP patients may be caused by a combined effect of impaired primary and secondary hemostasis.

Figure

Figure 1. Aggregation and platelet-derived extracellular vesicle -PEV- concentrations in immune thrombocytopenia -ITP- patients vs. healthy individuals.

To cite this abstract in AMA style:

Buntsma N, Gasecka A, Talsma S, Rytel J, Mądry K, Basak G, van der Pol E, Nieuwland R. Bleeding tendency in thrombocytopenic patients due to impaired defects in primary and secondary hemostasis [abstract]. https://abstracts.isth.org/abstract/bleeding-tendency-in-thrombocytopenic-patients-due-to-impaired-defects-in-primary-and-secondary-hemostasis/. Accessed November 30, 2023.

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