Pan-pseudothrombocytopenia: An unusual case of platelet clumping.

Abstract

A 39-year-old, healthy Asian female was admitted to the labor and delivery service for twin–twin transfusion syndrome. She was incidentally noted to have thrombocytopenia with a platelet count of 42 k/mm3 checked in an ethylenediaminetetraacetate (EDTA) vial. She was asymptomatic, without history of unexpected bleeding or bruising and normal platelet counts earlier in pregnancy. Both citrated and heparinized platelet counts were similarly suggestive of true thrombocytopenia. However, review of blood smears showed platelet clumping in all three tubes: EDTA (Image 1A), citrated (Image 1B), and heparinized (Image 1C). The patient's true platelet count was approximately 250 k/mm3 by manual count, well within the normal range. We concluded that this patient's thrombocytopenia was an in vitro artifact, commonly termed pseudothrombocytopenia. Blood smears showing platelet clumping in all three tubes: A, EDTA, B, citrated, and C, heparinized Pseudothrombocytopenia is mediated by anti-glycoprotein IIb/IIIa autoantibodies that result in platelet clumping when exposed to EDTA in vitro.1, 2 The effect is a lab artifact that results in a falsely decreased platelet count, but no clinical manifestations.3 The diagnosis is suspected when review of a peripheral blood smear from the EDTA tube confirms platelet clumping with a normal quantity of platelets by manual evaluation. The diagnosis may be confirmed if a repeat blood smear from a citrated tube resolves the clumping. However, in up to 17% of cases, the platelet clumping may persist in the citrated tube.4 In these instances, collection in a heparinized tube uniformly corrects the artifactual effects. We report the first case of pseudothrombocytopenia that persisted in both the citrated and heparinized tubes. The blood smear review remains important in the workup of thrombocytopenia despite the advent and use of automated blood cell counters. This diagnosis would have been missed without review of the blood smear, resulting in further unnecessary workup and inappropriate treatment. Nothing to report.