EDTA-dependent pseudo-thrombocytopenia is an artefact characterized by spuriously low platelet counts potentially occurring when using automated analyzers. This phenomenon is due to in-vitro platelet clumping caused by antiplatelet autoantibodies in EDTA-anticoagulated blood. Identifying such a condition is crucial to avoid misdiagnosis and mismanagement, resulting in excessive medical examinations and unnecessary treatments . Here, we report a case of transient pseudo-thrombocytopenia in a patient who had received autologous stem cell transplantation.
A 56-year-old male had been diagnosed in February 2016 with IgG λ multiple myeloma, Durie and Salmon stage II, international scoring system II. Induction therapy was based on VTD (bortezomib, thalidomide and dexamethasone) for three cycles achieving a complete remission. At that time, his blood counts were normal (Hemoglobin: 13 g/dl, white blood cells: 20 × 103/mm3, platelets: 419 × 103/mm3) and serum and urinary immunofixation were negative. In September 2016, an autologous stem cell transplantation was performed after conditioning with melphalan 200 mg/m2. The first evidence of thrombocytopenia was 5 days after stem cell infusion in the absence of any haemorrhagic event. At day +12, the lowest platelets count (platelets 3.2 × 103/mm3) was documented beside an almost complete neutrophil recovery (2.4 × 103/mm3). Until then, platelet transfusions had been carried out at days +8, +9, +10 and +12. Thrombocytopenia was initially interpreted as a delayed haematological recovery as anaemia and neutropenia coexisted. However, as shown in Fig. 1 at day +24, a persistent decrease of the platelet count (platelets 3.6 × 103/mm3) was observed, whereas haemoglobin and leucocyte counts were already normal. At that time a peripheral blood smear was performed and revealed large platelet clumps. To confirm the suspect of pseudo-thrombocytopenia, blood counts were repeated by using tubes with citrate and heparin, which demonstrated higher platelets counts (110 and 117 × 103/mm3, respectively). In December 2016, almost 3 months after autologous stem cell transplantation, the pseudo-thrombocytopenia spontaneously resolved. The patient is now in complete remission and his full blood counts are normal.
Pseudo-thrombocytopenia is rare artefact characterised by spuriously low platelet counts that occurs when EDTA reacts with harvested blood. It can be observed with electronic blood-counting machines and is determined by in-vitro clumping. Its prevalence ranges between 0.1 and 0.21% in both healthy controls and hospitalised study participants . Previous studies have shown that pseudo-thrombocytopenia is due to the potential ability of EDTA to dissociate the Ca2+-dependent platelet membrane glycoprotein IIb/IIIa heterodimer . Meanwhile, antiplatelet autoantibodies recognise the exposure of the epitopes on glycoprotein IIb/IIIa thus leading to the generation of platelet clumps, more readily at cold temperature. Although it is known that blood specimens anticoagulated with heparin or citrate can be used to guarantee a more accurate platelet count, the most accurate method to demonstrate platelet clumping is based on the evaluation of a peripheral blood smear [1,2].
The cause of this phenomenon is still unknown, whereas a possible acquired cause has been suggested, considering its occurrence in patients with sepsis, after allogenic transplantation or with autoimmune, neoplastic, cardiovascular and liver diseases. In the present case, a possible explanation could be identified in the immune regeneration, typically occurring after autologous stem cell transplantation. Several studies have demonstrated that a successful immune reconstitution is important to decrease posttransplant the risk of infection, relapse or secondary malignancy . In particular, special attention is paid to the reconstitution of CD4+ T lymphocytes, which are considered key players in many autoimmune diseases .
Pseudo-thrombocytopenia is a benign entity not requiring any treatment and not providing any clinical implication. However, the crucial relevance of recognizing such a condition clearly emerges in specific clinical scenarios. In the present case, the detection of thrombocytopenia after bone marrow transplantation could be potentially ascribed to many different causes including infections, thrombotic thrombocytopenic purpura, immune-mediated thrombocytopenic purpura, poor engraftment or disease relapse, most of which are conditions requiring a specific medical intervention. Therefore, the early diagnosis of pseudo-thrombocytopenia has undoubtedly avoided possible overexamination and overtreatment which may have had an impact on the clinical management of this patient. Further studies could offer a functional explanation for the occurrence of pseudo-thrombocytopenia in the context of the unique immunological milieu observed after stem cell transplantation.
Conflicts of interest
There are no conflicts of interest.
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* Alessandra Di Francesco and Annamaria Pasanisi equally contributed to this work.