This study found that baseline platelet levels and changes in levels were associated with subsequent mortality. 

This study explored the relationship between thrombocytopenia and COVID-19. Researchers reviewed the clinical and laboratory data of 383 patients in Wuhan. Among them, 87% were discharged and survived, and 13% died.

Thrombocytopenia at the time of admission was associated an almost three times as high mortality. Platelet count was an independent risk factor associated with mortality in a dose-dependent manner. Each 50 × 109/L in platelets was associated with a 40% decrease in mortality. Dynamic changes of platelets during hospitalization was also associated with death.