PMC9184712_01
Skin edema, platelet aggregates on the EDTA blood smear, and platelet count evolution in EDTA and citrate anticoagulated blood. Lower limb skin edema in patient 12 days after ChAdOx1 nCoV-19 vaccination, with spontaneous resolution after four months (A); Peripheral blood smear from the EDTA-anticoagulated patient's blood showing platelet aggregates (arrow) (B); Platelet counts in EDTA anticoagulation are shown in blue; platelet counts in citrate anticoagulation are shown in orange starting in August 2021. COVID-19 infection is indicated by a star, ChAdOx1 nCoV-19 and BNT162b2 vaccinations are shown by black arrow s (C).
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F1
A 46-years-old white female, smoker with pulmonary emphysema, sought medical consultation in mid-February 2021 after presenting progressive face and lower limbs edema (Figure 1A). Blood count using citrate anticoagulant showed normal platelet count, and peripheral blood smear of the EDTA sample showed platelet aggregates (Figure 1B). One month later, the blood counts on EDTA and citrate confirmed these findings (Figure 1C), and pseudothrombocytopenia was diagnosed.
EDTA induced platelets hyperreactivity but did not increase basal activity or heterotypic aggregation with leukocytes. Platelets were isolated from the patient and healthy donors' fresh blood collected with ACD or EDTA and analyzed by flow cytometry for surface expression of CD62p (A) and CD63 (B). Platelet-leukocyte aggregates were assessed by the percentage of CD41+ platelets among neutrophils (CD66b+) (C), total monocytes (CD14+) (D), Platelet reactivity was analyzed by the mean fluorescence intensity (MFI) of CD62p (E) and CD63 (F) after stimulation with thrombin at 0.05 and 0.5 U/mL. Bars represent the mean +- SEM, and each dot represents one individual. ACD: acid-citrate-dextrose.
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F2
Both ACD and EDTA samples showed no changes in platelet activation, as demonstrated by CD62p and CD63 surface expression (Figures 2A,B, respectively). Furthermore, no alterations were observed regarding platelet aggregation with neutrophils (Figure 2C) or monocytes (Figure 2D). However, isolated platelets from the patient's EDTA sample, but not ACD, presented hyperreactivity compared to healthy donors, as shown by CD62p and CD63 mean fluorescence intensity (MFI) in platelets stimulated with thrombin (Figures 2E,F).