Background: Essential thrombocythemia (ET) and polycythemia vera (PV) have an increased risk of both thrombosis and bleeding. Recent clinical studies have shown that patients with JAK2 gene mutation have a higher risk of thrombosis than those without mutation. However, the effect of JAK2 mutation on dynamics of thrombus formation in ET/PV is not well characterized.

Aims: To assess dynamics of thrombus formation under flow conditions in ET/PV.

Methods: We examined platelet thrombus formation on a collagen-coated microchip under flow conditions using total thrombus-formation analysis system (T-TAS). Whole blood from 48 patients including 36 ET, 12 PV patients and 20 healthy controls were subjected to T-TAS. T10 (time at the onset of thrombus formation) and T60-10 (time from T10 to occlusive thrombus formation) were evaluated. JAK2 mutation was determined by allele-specific PCR.

Results: The T10 in ET/PV patients was longer than that in control (184±195 sec vs 83±33 sec, p< 0.01), indicating delay in the onset of thrombus in ET/PV. In the ET/PV patients, T10 was negatively correlated with hematocrit, but not platelet count while T60-10 was negatively correlated with platelet count, but not hematocrit. T10 in patients with JAK2 mutation was shorter than T10 in patients without JAK2 mutation (139±153 sec vs 318±246 sec, p=0.03), suggesting faster start of thrombus formation in patients with JAK2 mutation. Von Willebrand factor activity was not associated with T10 or T60-10.

Conclusions: These results suggest that increased hematocrit and JAK2 mutation accelerate start of thrombus formation (T10) and increased platelet count promotes thrombus growth under flow conditions. These dynamics of thrombus formation may be involved in pathogenesis of hemostatic manifestations in ET/PV.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/assessment-of-thrombus-formation-under-flow-conditions-in-essential-thrombocythemia-polycythemia-vera/