RESUMO
Pseudothrombocytopenia by ethylenediaminetetraacetic acid (EDTA) is an infrequent phenomenon of in vitro platelet agglutination due to the presence of antiplatelet autoantibodies. It has no clinical significance, but misdiagnosis may lead to clinical or therapeutic decision-making. In this study we report a case of an 8-year-old boy with no history of platelet disorder presenting a low platelet count and a peripheral blood smear showing clumping of platelets by EDTA. The initial diagnosis hypothesis was of an idiopathic thrombocytopenic purpura, and an unnecessary bone marrow aspirate was made even though he did not have personal or family history of bleeding. A second sample collected in sodium citrate confirmed the pseudothrombocytopenia by EDTA. In conclusion, the laboratory should enhance a strong relationship with clinicians trying to avoid misunderstandings as that reflected in this case report. It should be reminded that, in those cases where a pseudothrombocytopenia by EDTA is suspected, a blood smear is mandatory to confirm platelet clumps and blood must be tested anticoagulated with another anticoagulant (i.e., sodium citrate or heparin).
