BLEEDING-TIME AND PLATELET-FUNCTION IN ESSENTIAL THROMBOCYTHEMIA AND OTHER MYELOPROLIFERATIVE SYNDROMES

Bleeding time (BT) and platelet function tests have been widely used i n patients with essential thrombocythemia (ET), with the aim to suppor t diagnosis and to identify laboratory predictors of haemorrhagic and thrombotic complications. BT is significantly prolonged in 7-19% of ET patients and several functional abnormalities have been observed in p latelet structure, biochemistry and survival. However, the attempt to relate these in vivo and in vitro platelet dysfunctions with diagnosis or clinical sequelae has been generally disappointing. Therefore, BT and platelet function tests are currently not recommended in the initi al evaluation or during the follow-up of patients with ET, unless in t he setting of a clinical or biological study. A noteworthy exception i s represented by a subset of patients characterized by very high plate let count (>1500 x 10(9)/L) and bleeding symptoms, who can have an acq uired von Willebrand disease. In these cases, prolonged BT and abnorma l multimeric pattern of von Willebrand factor are useful for diagnosin g and monitoring this acquired hemorrhagic disease. BT and platelet fu nction tests should be included in the baseline evaluation of ET patie nts enrolled in prospective clinical trials aiming assess their predic tive role on clinical end-points.