PB0692 - Effect of thrombopoietin receptor agonists on coagulation factors, von Willebrand factor and ADAMTS13 in patients with immune thrombocytopenia.

Monday, June 24, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

Lamya Garabet

Postdoctoral researcher
Center for Laboratory Medicine, Østfold Hospital Trust
Grålum, Ostfold, Norway

Co-Author(s)

Waleed Ghanima

Head of Research and Consultant Hematologist
Department of Medicine, Østfold Hospital Trust
Kalnes, Ostfold, Norway
AH

Andreas Hillarp

Consultant
Oslo University Hospital
Oslo, Oslo, Norway
�M

Åse-Berit Mathisen

Biomedical Engineer
Ostfold Hospital Trust
Grålum, Ostfold, Norway
SL

Stine Lae

Biomedical Engineer
Ostfold Hospital Trust
Grålum, Ostfold, Norway
MS

Marie Skogstad Le

Biomedical Engineer
Oslo University Hospital
Oslo, Ostfold, Norway
JB

James Bussel

Consultant
Weill Cornell Medicine
New York, New York, United States
CH

Carola Henriksson

Consultant
Oslo University Hospital
Oslo, Oslo, Norway

Background: Despite low platelet count and increased bleeding risk in immune thrombocytopenia (ITP), ITP is also a prothrombotic disorder. Thrombopoietin receptor agonists (TPO-RA) are effective treatment in ITP, but nevertheless are associated with increased thrombotic risk. The underlying mechanisms for the prothrombotic nature of ITP especially post-TPO-RA-treatment are not fully characterized.

Aims: To measure von Willebrand factor (VWF), ADAMTS13 and coagulation factors in ITP and to study the effect of TPO-RA-treatment on these parameters.

Methods: Blood samples from primary ITP patients (n=15) before initiating TPO-RA-treatment and after achieving response, defined as platelet count >50.109/L, and healthy controls (n=15) were obtained. We measured VWF antigen (VWF:Ag) and activity (platelet GPIb binding (VWF:GPIbR) and collagen binding activity (VWF:CB)), and ADAMTS13 activity. Coagulation factors (F)V, FVII, FVIII and FIX were measured with one stage assay; FVIII was also measured with chromogenic substrate assay.

Results: Median age was 58 years (IQR:43–68) for patients, 55 years (IQR:45–58) for controls, and 47% were females in both groups. We found no significant differences in FV, FVII, FVIII and FIX activity, or in VWF antigen or activity between ITP patients and controls (Table 1). ADAMTS13 activity was significantly lower in ITP patients, both before TPO-RA-treatment (p=0.036) and after treatment (p=0.019) compared with controls. VWF:CB, FVIII and FIX activity decreased after TPO-RA-treatment compared with before treatment (Table 2).

Conclusion(s): We found no significant difference in the coagulation factors or VWF between ITP patients before TPO-RA-treatment and controls. However, ADAMTS13 was significantly lower in ITP patients compared with controls, and did not change after TPO-RA-treatment. Low ADAMTS13 may contribute to the procoagulant profile in ITP patients. TPO-RA-treatment was associated with a decrease in VWF:CB, FVIII and FIX activity, thus may not contribute to a further increase in the procoagulant profile in these patients.