PF 4 versus beta TG as evidence for platelet activation in myeloproliferative disorders.

19 patients with MPD have been studied. As described in normals, an age-related increase in beta thromboglobulin (beta TG) release is observed. Such release, however, is greater in patients with myeloproliferative disorders (MPD). MPD seem therefore to cause platelet activation, allowing an earlier and more evident manifestation of physiologic ageing phenomena. PF 4 levels are near zero both in controls and patients, regardless of platelet number. This suggests that increased levels of PF 4 represent only a laboratory artifact, caused by platelet activation in vitro. Mean ability in producing thromboxane B2 (TxB2) is increased, but is perfectly normal in patients with normal platelet count and decreased in 3 thrombocythaemic patients, who seem to present an increased thrombotic risk. TxB2 is reduced almost to zero by the administration of aspirin plus dipyridamole; contrarily, all other parameters were unaffected, either by such drugs or by AD 6, a new coumarin derivative with antiplatelet properties.