Hyperresponsive Platelets and a Reduced Platelet Granule Release Capacity Are Associated with Severity and Mortality in COVID-19 Patients

Background Coronavirus disease 2019 (COVID-19) is often associated with mild thrombocytopenia and increased platelet reactivity. Objective The aim of the current study was to investigate the adenosine triphosphate (ATP) release kinetics of platelets in hospitalized SARS-CoV-2-infected patients. Methods We studied time-dependent platelet activation in whole blood by monitoring the ATP release kinetics upon stimulation with a PAR1 receptor agonist in 41 hospitalized critically ill COVID-19 patients, 47 hospitalized noncritically ill COVID-19 patients, and 30 healthy controls. Results Our study demonstrated that platelets of critically ill COVID-19 patients were hyper-responsive with a shorter platelet response time (PRT) and a reduced platelet granule release capacity (GRC), probably due to chronic activation. The median PRT of COVID-19 patients admitted to the critical care unit was 10 and 7 seconds shorter than the median PRT in healthy controls and noncritical COVID-19 patients, respectively. Both PRT and GRC were also associated with D-dimer (Spearman r [r s] = −0.51, p < 0.0001 and r s = −0.23, p < 0.05), C-reactive protein (CRP) (r s = −0.59, p < 0.0001 and r s = −0.41, p < 0.01), and neutrophil-to-lymphocyte ratio (NLR) (r s = −0.42, p < 0.0001 and r s = −0.26, p < 0.05). Moreover, an increased PRT and a reduced GRC were associated with an increased mortality (odds ratio [OR]: 18.8, 95% confidence interval [CI]: 6.5–62.8, p < 0.0001 and OR: 4.0; 95% CI: 1.6–10.4, p < 0.01). These relationships remained significant after adjustment for age, sex, D-dimer, CRP, and NLR. Conclusion Using an accessible agonist-induced platelet granule ATP release assay, we show that platelet hyper-responsiveness and reduced platelet GRC in COVID-19 patients were associated with critical illness and mortality.