Results of an international survey of opinions on the definitions and treatments for heparin-induced thrombocytopenia: communication from the ISTH SSC Subcommittee on Platelet Immunology

HIT is rare, affecting fewer than 1 in 1500 hospital admissions. Despite the increasing adoption of new therapies in HIT such as direct oral anticoagulants and pooled immunoglobulins, there is limited high quality evidence to guide clinicians. Numerous uncommon presentations of HIT and HIT-like entities have recently been recognised and a harmonised approach to their classification is required to better study them. We present the results of an international survey of opinions from experts and practitioners in the field of platelet immunology regarding the role of DOACs in HIT, novel definitions of subclassifications of HIT-like PF4-immune conditions (spontaneous autoimmune HIT, persistent autoimmune HIT, and treatment refractory HIT), and the role for intravenous immunoglobulins in the treatment paradigm of HIT and these HIT-like conditions. From n=102 survey responses, there was broad acceptance of rivaroxaban (74.5%) and apixaban (73.5%) even before platelet recovery; as well as for IVIg in the management of spontaneous (85.6%), persistent (83.7%) and treatment refractory HIT (87.4%). With this mandate for harmonizing terminologies and treatment approaches in special situations without robust clinical data owing to their rarity, we plan to conduct a robust survey, establish international consensus, and draft management guidelines for HIT and PF4-immune diseases in the near future.