Assessment of Platelet Thrombus Formation under Flow Conditions in Adult Patients with COVID-19: An Observational Study

Background Coronavirus disease 2019 (COVID-19) is associated with systemic inflammation, which may dysregulate platelet function. Total Thrombus-Formation Analysis System (T-TAS) is a flow-chamber device that analyses platelet-mediated thrombus formation in capillary channels through the following parameters: (1) the area under the flow-pressure curve (AUC), (2) occlusion start time (OST), time needed to reach OST, and (3) occlusion time (OT), time needed to reach the occlusion pressure. Methods and Findings Sixty-one COVID-19 patients admitted to intensive, subintensive, and low intensive care were prospectively enrolled according to the time of admission: group A (up to 8 days) ( n =18); group B (from 9 to 21 days) ( n =19), and group C (>21 days) ( n =24). T-TAS measurements were performed at enrolment and after 7 days. Median OST was similar among groups. AUC was lower in group A compared to B ( p =0.001) and C ( p =0.033). OT was longer in group A compared to B ( p =0.001) and C ( p =0.028). Platelet count (PC) was higher in group B compared to A ( p =0.024). The linear regression showed that OT and AUC were independent from PC in group A (OT: 0.149 [95% confidence interval [CI]: -0.326 to 0.624], p =0.513 and AUC: 0.005 [95% CI: -0.008 to 0.017], p =0,447). In contrast, in group B, PC was associated with OT (-0.019 [-0.028 to 0.008], p =0.023) and AUC (0.749 [0.358-1.139], p =0,015), similarly to group C. Conversely, patients with different illness severity had similar T-TAS parameters. Conclusion COVID-19 patients display an impaired platelet thrombus formation in the early phase of the disease compared to later stages and controls, independently from illness severity.