Influence of platelet and white blood cell counts on major thrombosis - analysis from a patient registry in essential thrombocythemia.

OBJECTIVES

Although guidelines recommend normalization of platelet counts as an appropriate endpoint for treatment in high-risk essential thrombocythemia (ET), retrospective studies could not prove a correlation of diagnostic platelet counts with an increased thrombotic rate. There is, however, an increasing evidence that leukocytosis is an important risk factor for arterial thrombosis in myeloproliferative neoplasms.

METHODS

This study considers the Austrian cohort of a European registry regarding the platelet-lowering therapeutic anagrelide. Influence of platelet and white blood cell (WBC) counts on thrombotic risk was assessed.

RESULTS

Using the calculated cutoffs of 574.5 G/L for platelets and 8.48 G/L for WBC counts, respectively, the Cox regression analysis revealed a clear influence of elevated platelets (P = 0.008) and WBC counts (P = 0.011) on the occurrence of major thrombotic events. The time to a major thrombotic event was shortest (P < 0.001) and the frequency related to 100 patient-years was highest (P = <0.001) when both platelet and WBC counts ranged above the calculated cutoffs.

CONCLUSION

Our data add evidence to the impact of platelet and WBC counts on thrombosis in ET. We suspect a particular interaction between platelets and WBC which might be based on a biological interplay depending on particular cell counts.