Not yet to be born - A clinical case of pseudothrombocytopenia in a pregnant woman
Authors: A. C. B. Marques, A. V. D. Barros, J. S. Matias, M. Manacas, F. Carrico, A. Miranda
Journal: HemaSphere (2021)

Background: Pseudothrombocytopenia (PTCP) is a platelet count (PC) erroneously below the reference value, usually under150x109/L, due to platelet aggregation or platelet satellitism that happens in vitro triggered by the presence of an anticoagulant, mostly seen with EDTA. This phenomenon happens due to the binding of autoantibodies to glycoprotein IIb/IIIa in the presence of EDTA. Aims: The authors present a clinical case of pseudothrombocytopenia. Methods: 32-year-old pregnant woman, gesta 5, para 4, at 36 weeks and 2 days was admitted to the Obstetrics Emergency Room (OER) with complains of low back pain, cramps, chills, vomiting and nausea with1 day evolution. The patient denied fever, cough, respiratory difficulty or urinary symptoms. There was no known epidemiological context for SARS-CoV-2 infection. Obstetric past history of 4 previous eutocic deliveries, 2 of them were preterm labours at 27th and 34th week of gestation. She had been medicated in outpatient care with vaginal progesterone. At clinical observation in the OER the patient was hemodynamically stable with no significant clinical changes, only showing a dubious right Murphy sign. Analytically, revealed thrombocytopenia of126x109/L, lymphopenia of 0,34 x109/L and C-RP: 3,93mg/dL;the remaining inflammatory parameters were within reference values as well as renal function and liver damage analytes. Urine dipstick test revealed Ketone bodies:150mg/dL;Proteins: 25mg/dL;Leucocytes:100 cell/μL;Erythrocytes:10 cell/μL;Nitrites: negative. SARS-CoV-2 RT-PCR test was positive. Cardiotocography (CTG) showed a normal pattern, with fetal heart rate of150-160 bpm and irregular and sparse uterine contractility. The patient was proposed for hospitalization with CTG monitoring and started empirical antibiotherapy with cefuroxime for a presumed acute pyelonephritis. Prophylactic enoxaparin was started on the 2nd day. The pregnant woman remained clinically stable, analytically highlighting a progressive decrease in PC from the 2nd day on, with PC of 85x109/L. On the 4th day of hospitalization with thrombocytopenia of11x109/L, a blood smear and the sFlt-1/PlGF ratio ongoing, a variety of different diagnosis were raised, such as pre-eclampsia, HELLP syndrome, autoimmune disorders, idiopathic thrombocytopenic purpura, heparin induced thrombocytopenia (HIT) or COVID-19-induced thrombocytopenia. At this point, our laboratory was contacted in order to confirm the low PC, since a labour induction was a possibility. Results: HIT test proved to be negative and the blood smear revealed many and huge platelet aggregations. To confirm the PC our laboratory advised a new blood collection in a trisodium citrate solution (S-Monovette. Citrate) and in Mg2+ compound (S-Monovette. ThromboExact) collection tubes, which revealed a PC of 31x109/L and123x109/L, respectively. On the 5th day she was discharged. After COVID-19 infection cure, the PC values remained significantly different when measured in an EDTA and in Mg2+ compound collection tubes. The delivery happened, later, at 39 weeks of gestation. Summary/Conclusion: The identification of a PTCP allowed us to avoid an iatrogenic preterm labour. When confronted with a patient with no signs or symptoms of bleeding or haemorrhagic dyscrasia and no past history of thrombocytopenia, PTCP should be considered as one of the differential diagnosis. It is estimated that approximately 0.1% of the whole population has antiplatelet autoantibodies triggered by EDTA. Early detection of this phenomenon may avoid an extensive investigation and unnecessary therapeutic procedures.