Role of Molecular Drivers in Coagulation By Integral Assessment in Primary Myelofibrosis Patients
Authors: Efremova Elizaveta , Matvienko Olesya , Korsakova Natalya , Fominykh Mikhail , Silina Natalya , Papayan Ludmila , Polushkina Lyubov , Motyko Ekaterina , Martynkevich Irina , Shuvaev Vasily , Voloshin Sergei 
Published: October 2019

Abstract
Background: Thrombosis in Primary Myelofibrosis (PMF) is one of the main but not fully covered problem. Thrombotic complications in PMF occur more frequently than in general population and could result to morbidity and lethality of patients. Several previous studies have demonstrated different thrombotic rates related to type molecular driver mutation (JAK2V617F, CALR, MPL) in myeloproliferative neoplasms, but this fact now is not fully understood. The standard clotting tests cover only initial stages of coagulation and could not evaluate anticoagulant system. Its results are not varied in PMF patients with different mutations. We have interested and initiated study of the coagulation system in PMF patients with integral hemostasis test - Calibrated Automated Thrombography (CAT). Here we present the results of pilot study group assessment.
Aim: to investigate of the coagulation system in PMF patients with different molecular driver mutations (JAK2V617F, CALR, MPL) using thrombin generation test.
Methods: The study included 13 MF patients (26 - 71 years, median = 40). There were 11 females and 2 males. Nine patients were JAK2V617F positive, 3 had CALR mutations and one patient was MPL-mutated. Thrombin generation was assessed by calibrated automated thrombinography (CAT) according to Hemker et al. Assessments were conducted in platelet poor plasma (PPP) with or without presence of thrombomodulin (PPP reagent +/- TM) as an activator of protein C system. The following parameters were evaluated: endogenous thrombin potential (ETP, nM*min), peak thrombin (Peak, nM), lag-time (Lag, min), and time to peak (TTP, min). Sensitivity ETP and Peak for TM were calculated as percent of decreasing of these parameters after adding to assay of TM (S ETP, % and S Peak, % respectively). STATISTICA 6.0 package was used in data analysis. Results were presented as median (Me) with 95% confidence intervals (CI).
Results: ETP was highest in JAK2V617F patients (1213.57; min 781.60-max 1781.26 nM*min), intermediate in CALR (1058.47; min 933.14-max 1190.79 nM*min) and lowest in MPL group (972.49 nM*min). However, the Peak was higher in CALR (207.57; min 165.63-max 235.36 nM) than in JAK2V617F (160.9; (min 94.38-max 317.11 nM) and MPL (136.19 nM). We have observed disruption of protein C functioning in JAK2V617F (S-ETP 34%, min 8.65%-max 68.73%; S-Peak 20%, min 0.01%-max 44.64%) and MPL (S-ETP 46%; S-Peak 24%) groups compared to CALR patients (S-ETP 6.4%, min 2.5%-max 9.2%; S-Peak 1.8%, min 0.87%-max 1.8%).
Conclusion: The results of thrombin production were differed in relation to driver mutation type. JAK2V617F-patients produced more thrombin and have protein C system dysfunction. It could be serve as an explanation of higher risk of thrombosis in MF patients with JAK2V617F mutation. The yielded results force us to continue research to confirm our findings on representative sample of PMF patients.

Disclosures
No relevant conflicts of interest to declare.