Immature platelets in patients hospitalized with Covid-19

Coronavirus disease 2019 (Covid-19) is associated with high incidence of venous and arterial thromboembolic events. Currently, there are no markers to guide antithrombotic therapy in Covid-19. Immature platelets represent a population of hyper-reactive platelets associated with arterial events. This prospective study compared consecutive Covid-19 patients (n = 47, median age = 56 years) to patients with acute myocardial infarction (AMI, n = 100, median age = 59 years) and a group of stable patients with cardiovascular risk factors (n = 64, median age = 68 years). Immature platelet fraction (IPF) and immature platelet count (IPC) were determined by the Sysmex XN-3000 auto-analyzer on admission and at subsequent time-points. IPF% on admission was higher in Covid-19 than the stable group and similar to the AMI group (4.8% [IQR 3.4–6.9], 3.5% [2.7–5.1], 4.55% [3.0–6.75], respectively, p = 0.0053). IPC on admission was also higher in Covid-19 than the stable group and similar to the AMI group (10.8 × 10⁹/L [8.3–18.1], 7.35 × 10⁹/L [5.3–10.5], 10.7 × 10⁹/L [7.7–16.8], respectively, P < 0.0001). The maximal IPF% among the Covid-19 group was higher than the stable group and similar to the AMI group. The maximal IPC in Covid-19 was higher than the maximal IPC in both the stable and AMI groups (COVID-19: 14.4 × 10⁹/L [9.4–20.9], AMI: 10.9 × 10⁹/L [7.6–15.2], P = 0.0035, Stable: 7.55 × 10⁹/L [5.55–10.5], P < 0.0001). Patients with Covid-19 have increased immature platelets indices compared to stable patients with cardiovascular risk factors, and as the disease progresses also compared to AMI patients. The enhanced platelet turnover and reactivity may have a role in the development of thrombotic events in Covid-19 patients.