LAUSR

BACKGROUND Platelet activation at the early stage of COVID-19 is poorly described. The need for antiplatelet therapy in patients with COVID-19 remains controversial. We characterized the platelet activation profile in hospitalized patients at the early stage of COVID-19 using the modified prothrombinase Platelet Activation State (PAS) assay. METHODS Sixteen patients admitted to the emergency department of the IRCCS San Raffaele Scientific Institute (Milano, Italy) between February 8 and April 2021 were enrolled. All patients presented with respiratory symptoms and tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Platelet activation was measured via the PAS assay within 24 hours from patients' hospital admission. Data were compared with those measured in n=24 healthy subjects (controls). RESULTS Platelet activation was significantly higher in COVID-19 patients with respect to controls (PAS = 0.63 [0.58-0.98]% vs. 0.46 [0.40-0.65]%, respectively; p=0.03). Of note, highest PAS values were measured in the two patients with the worst clinical outcome, i.e., death because of respiratory failure (PAS = 2.09% and 1.20%, respectively). No differences in standard coagulation parameters were noted between these two patients and those who were later discharged home. CONCLUSIONS This study provides evidences of significant platelet activation state at the early stage of COVID-19 and suggests that the patient-specific platelet activation profile is a reliable clinical marker to stratify COVID-19 patients at high risk of poor clinical outcome who might potentially benefit from antiplatelet therapy.