PB0174 - Activated Factor XI as Activator of Thrombin Generation to Increase Assay Sensitivity

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Ryanne Astrid Arisz, MSc.

PhD student
Department of Hematology, Erasmus MC, Erasmus University Medical Center Rotterdam, Rotterdam, the Netherlands.
Rotterdam, Zuid-Holland, Netherlands

Co-Author(s)

Tv

Tessa van Lienden

Intern
Department of Hematology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.
Rotterdam, Zuid-Holland, Netherlands
Romy De Laat-Kremers, PhD

Post-doctoral Research Project Leader
Department of Data Analysis and Artificial Intelligence, Synapse Research Institute, Maastricht, the Netherlands
Maastricht, Limburg, Netherlands
JE

Jeroen C.J. Eikenboom

Professor, Internist, Head of Div. T&H
Department of Internal Medicine, Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
Leiden, Zuid-Holland, Netherlands
SS

Saskia E.M. Schols

Internist-hematologist
Department of Hematology, Radboud university medical center, Nijmegen, The Netherlands. Hemophilia Treatment Center Nijmegen – Eindhoven – Maastricht, The Netherlands
Nijmegen, Gelderland, Netherlands
Moniek P.M. de Maat, PhD

Professor
Department of Hematology, Erasmus University Medical Center Rotterdam, Rotterdam, The Netherlands
Rotterdam, Zuid-Holland, Netherlands

Background: Haemophilia A is an X-linked genetic disorder, leading to a reduced factor VIII (FVIII) activity. FVIII activity levels are often used to classify disease severity. However, FVIII activity levels do not always correlate with bleeding tendency. The thrombin generation assay (TGA) may be a robust assay to predict interindividual bleeding risk, but the sensitivity for low FVIII levels is limited when activated with tissue factor (TF). Activated factor XI (FXIa) has been proposed to increase the sensitivity of the fluorescent signal in the TGA.

Aims: To evaluate if TGA is more sensitive for low FVIII activity levels with FXIa as activator, when compared to activation with TF.

Methods: Platelet poor normal pooled plasma, FVIII deficient plasma (Siemens) or a mix of both plasma’s were used to obtain 0%, 1%, 5%, 10% and 100% FVIII plasma concentrations. A low concentration of tissue factor (1pM) or 0.22 nM activated FXIa, together with calcium and phospholipids, were used to activate the TGA using the calibrated automated thrombogram (CAT; Stago). Results were analysed with the Thrombinoscope software.

Results: Activation with 0.22 nM FXIa resulted in 196%, 335%, 376%, and 455% higher peak heights, compared to activation with 1 pM TF for plasma samples with 1%, 5%, 10%, and 100% FVIII, respectively. The endogenous thrombin potential (ETP) and the lag time did not change despite the variation in plasma FVIII levels after activation with either TF or FXIa.

Conclusion(s): In conclusion, activation with FXIa leads to an increased signal in the TGA compared to activation with TF, especially for FVIII activity levels < 5%. With this alternative activator, the TGA is a promising tool to measure thrombin generation parameters in severe haemophilia A patients. More accurate predictors of bleeding will contribute to personalised treatment for these patients.