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Master Thesis

Comparaison d’un test automatisé de dosage de Willebrand par rapport au test par agrégométrie chez les patients thrombocytaires porteurs de syndrome myéloprolifératif

Abstract : Background: VWF is composed of multimers and the high-molecular-weight multimers (HMWM) carry the most important hemostastic effect. Patients with myeloproliferative neoplasms (MPN) and high platelet count (> 1500 G/L) are at risk of bleeding because of a decrease in HMWM, i.e. acquired von Willebrand disease. This is suspected when VWF ristocetin cofactor activity (VWF:RCo) is decreased. For functional assessment of VWF, aggregometry (RCo(Agg)) is considered to be the gold standard. However, this assay suffers from poor reproducibility and sensitivity at low levels of VWF and is labour intensive. Various assays for determination of VWF adhesive function using different methodologies have been developed in recent years. Aims: To compare the performance of HemosIL RCo, Werfen® versus aggregometry in patients with thrombocytosis (platelets > 450G/L) in the context of MPN (T-MPN) and in patients with secondary thrombocytosis (ST). Methods: samples from 33 patients with MPN and 18 patients with ST were evaluated by using RCo(Agg) and RCo(IL) assays. VWF antigen level (VWF:Ag), distribution of VWF multimers by electrophoresis and VWF binding capacity to collagen (CB) were also analysed for each patient. Results: In T-MPN and ST patients, there was a significant difference between the two techniques for RCo and RCo/Ag ratio (p < 0.0001 and p < 0.0001). A majority of T-MPN patients (23/33) had RCo/Ag ratio < 0.6 with HemosIL assay but not with aggregometry. In ST patients, 6/18 had discordant results. Among T-MPN patients with discordant results, 7 had actually a decrease in HMWM and/or CB < 0.6 versus none among the 6 ST patients with discordant results. There was a slight correlation between RCo(IL)/Ag ratio and platelet count in T-MPN patients but not in ST patients. Conclusion: hemosIL RCo reagent seems to be more sensitive than aggregometry to detect a change in the profile of HMWM in T-MPN patients.
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Submitted on : Tuesday, September 22, 2020 - 2:55:03 PM
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Pierre Laporte. Comparaison d’un test automatisé de dosage de Willebrand par rapport au test par agrégométrie chez les patients thrombocytaires porteurs de syndrome myéloprolifératif. Sciences du Vivant [q-bio]. 2020. ⟨dumas-02945674⟩

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