Categorization of anti-PF4 antibody disorders. The 4 identified conditions related to HIT presentation. Differentiation is related to the presence of heparin-dependent or heparin- independent anti-PF4 antibodies. Classical HIT/a HIT require stopping heparin, a change in anticoagulation, and occasionally further therapy such as high-dose IVIg. Conversely, VITT or VITT-like disorder require intensive immunomodulatory therapy, such as plasma exchange (PEX).