[Sudden onset of EDTA-dependent pseudothrombocytopenia in a patient scheduled for open heart surgery].

A 60-year-old woman scheduled for mitral and aortic valve replacement had sudden onset of thrombocytopenia without clinical symptoms. The platelet count was found to decrease after the sampling. Microscopic examinations confirmed platelet aggregations. Changing anticoagulant added to blood samples from EDTA to heparin resolved such platelet aggregations. This phenomenon was diagnosed as demonstrating EDTA-dependent pseudothrombocytopenia and the operation was performed as scheduled without platelet transfusion. Postoperative course was almost uneventful and the patient was discharged on 26th day after surgery. EDTA-dependent pseudothrombocytopenia must be ruled out when patients have thrombocytopenia without certain causes such as infections, drugs, or autoimmune diseases.