[EDTA-induced pseudothrombocytopenia]

EDTA-induced pseudothrombocytopenia is a laboratory artifact caused in vitro by platelet aggregation, due to IgG or IgM class antibodies reacting with antigenic binding site of the GP IIb glycoprotein. Pseudothrombocytopenia is rarely found (about 1% of platelets counts), but must be considered in the differential diagnosis of thrombocytopenia, since it could lead to useless investigations and therapies. We report three patients with pseudothrombocytopenia, one of whom underwent bone marrow biopsy and danazol treatment, before establishing the correct diagnosis. The absence of hemorrhagic manifestations with persisting low platelets counts led to a re-examination of peripheral blood smear and to the diagnosis of pseudothrombocytopenia. Therefore a morphological platelets evaluation and their count on citrate-anticoagulated blood must be performed in every patient under assessment for thrombocytopenia.