It was also noticed that HIT antibodies and a progressive decrease in platelets occurred in heparin-naïve patients (i.e., before CRRT or other heparin exposure), and even in non-ICU patients, suggesting that a spontaneous HIT might occur in COVID-19 patients, probably related to the formation of PF4 tetrameric complexes during viral or secondary bacterial infection. Here, PF4 is linked to COVID-19.