PF4 and deep vein thrombosis: While there remains controversy over the clinical significance of a low-titer anti-PF4, due the limited access to functional assays, we propose that patients with a positive anti-PF4, markedly elevated D-dimer, thrombocytopenia and thrombosis within the time frame of VITT, regardless of the type of vaccine, be treated with the same urgency and consideration as cases of confirmed VITT.