PB0331 - Bleeding tendency in thrombocytopenic patients due to impaired defects in primary and secondary hemostasis

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Naomi C. Buntsma, MSc

PhD Candidate
Amsterdam UMC
Amsterdam, Noord-Holland, Netherlands

Co-Author(s)

AG

Aleksandra Gasecka

Assistant Prof
Medical University of Warsaw
Warsaw, Mazowieckie, Poland
ST

Sytske Talsma

Student
Laboratory of Experimental Clinical Chemistry, Amsterdam UMC
Amsterdam, Noord-Holland, Netherlands
JR

Jagoda Rytel

MD
Department of Hematology, Oncology and Internal Medicine, Medical University of Warsaw, Warsaw, Poland
Warsaw, Mazowieckie, Poland
KM

Krzysztof Mądry

MD
Department of Hematology, Oncology and Internal Medicine, Medical University of Warsaw, Warsaw, Poland
Warsaw, Mazowieckie, Poland
GB

Grzegorz Basak

Professor
Department of Hematology, Oncology and Internal Medicine, Medical University of Warsaw, Warsaw, Poland
Warsaw, Mazowieckie, Poland
Ev

Edwin van der Pol

Assistant Prof
University of Amsterdam
Amsterdam, Noord-Holland, Netherlands
RN

Rienk Nieuwland

Research Associate
University of Amsterdam
Amsterdam, Noord-Holland, Netherlands

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.