Effects of anagrelide on platelet factor 4 and vascular endothelial growth factor levels in patients with essential thrombocythemia

The management of essential thrombocythemia (ET) includesalkylating agents, hydroxyurea (HU) and interferon-a (IFN-a)alone or in combination with anti-aggregants (Spivak et al,2003). It has been demonstrated that ET patients receivingcytoreduction and anti-aggregants show increased plateletfactor 4 (PF4) levels despite clinical remission (Bellucci et al,1993). Anagrelide is a platelet-lowering drug that inhibitsplatelet aggregation (Spivak et al, 2003). Therefore, we eval-uated the platelet count and PF4 levels in ET patients treatedeither with HU, IFN-a or anagrelide in combination with anti-aggregants. Activated platelets release vascular endothelialgrowth factor (VEGF), which is increased in ET (Mesa et al,2000). Thus, we also determined the corrected platelet VEGFlevel (VEGF