Impairment of platelet function in both mild and severe COVID‐19 patients

Abstract

SummaryAbnormalities of platelet function were reported in patients with severe COVID‐19 (severe‐C), but few data are available in patients with mild COVID‐19 (mild‐C) and after COVID‐19 recovery. The aim of this study was to investigate platelet parameters in mild‐C patients (n = 51), with no evidence of pneumonia, and severe‐C patients (n = 49), during the acute phase and after recovery, compared to 43 healthy controls. Both mild‐C and severe‐C patients displayed increased circulating activated platelets, low δ‐granule content (ADP, serotonin), impaired platelet activation by collagen (light transmission aggregometry) and impaired platelet thrombus formation on collagen‐coated surfaces under controlled flow conditions (300/s shear rate). The observed abnormalities were more marked in severe‐C patients than in mild‐C patients. Overall, 61% (30/49) of mild‐C and 73% (33/45) of severe‐C patients displayed at least one abnormal platelet parameter. In a subgroup of just 13 patients who showed no persisting signs/symptoms of COVID‐19 and were re‐evaluated at least 1 month after recovery, 11 of the 13 subjects exhibited normalization of platelet parameters. In conclusion, mild abnormalities of platelet parameters were present not only in severe‐C but also, albeit to a lesser extent, in mild‐C patients during the acute phase of COVID‐19 and normalized in most tested patients after clinical recovery.