Thrombocytopenias: a clinical point of view.

Abstract

The definition of thrombocytopenia is not unequivocal, since it is sometimes indicated as less than 100×109/L and sometimes as less than 150×109/L; furthermore, it is considered severe if the platelet count is below 30×109/L, moderate if it is between 30×109/L and 50×109/L, and mild (and usually asymptomatic) if above 50×109/L1. In clinical practice, the finding of thrombocytopenia is common and often casual. Only in the minority of cases it is found following bleeding or, in complete contrast, after thromboembolic events that can occur in the antiphospholipid syndrome2 and in heparin-induced thrombocytopenia3. The first thing to exclude when thrombocytopenia has been found incidentally, in the absence of clinical symptoms, is the possibility of a pseudothrombocytopenia due to in vitro agglutination of platelets in blood collected into tubes containing EDTA4. This event occurs in about one case in every 1000 healthy individuals and has no clinical significance. It is also worth excluding so-called “platelet satellitism”, due to adhesion of platelets to polymorphonuclear cells, a phenomenon that can be identified by examining a peripheral blood smear5. An examination of a peripheral blood smear is also useful for the diagnosis of congenital thrombocytopenias, which can be found for the first time in adults who have no or only very few symptoms: the correct diagnosis of these conditions will avoid inappropriate treatments.