PF4 and Venous thrombosis: In addition to these recent case reports, a retrospective analysis conducted on 188 consecutive patients with thrombocytopenia and/or thrombosis studied before the COVID-19 pandemic and with a laboratory pattern suggestive of VITT, i.e., the presence of anti-PF4/heparin IgG, showed that 13 tested positive by PIPA, highlighting the existence of VITT-like antibodies even before the COVID-19 pandemic and the vaccination campaign [64].