Heparin-induced thrombotic thrombocytopenia (HITT) and vaccine-induced immune thrombotic thrombocytopenia (VITT): Similar but different

Emmanuel J Favaloro, Leonardo Pasalic

Research output: Book chapter/Published conference paperChapter (peer-reviewed)peer-review

2 Citations (Scopus)

Abstract

Heparin-induced thrombocytopenia (HIT) represents an autoimmune process whereby antibodies are formed against heparin in complex with platelet factor 4 (PF4) after heparin administration. These antibodies can be detected by a variety of immunological assays, including ELISA (enzyme-linked immunosorbent assay) and by chemiluminescence on the AcuStar instrument. However, pathological HIT antibodies are those that activate platelets in a platelet activation assay and cause thrombosis in vivo. We would tend to call this condition heparin-induced thrombotic thrombocytopenia (HITT), although some workers instead use the truncated abbreviation HIT. Vaccine-induced (immune) thrombotic thrombocytopenia (VITT) instead reflects an autoimmune process whereby antibodies are formed against PF4 after administration of a vaccine, most notably adenovirus-based vaccines directed against COVID-19 (coronavirus disease 2019). Although both VITT and HITT reflect similar pathological processes, they have different origins and are detected in different ways. Most notable is that anti-PF4 antibodies in VITT can only be detected immunologically by ELISA assays, tending to be negative in rapid assays such as that using the AcuStar. Moreover, functional platelet activation assays otherwise used for HITT may need to be modified to detect platelet activation in VITT.
Original languageEnglish
Title of host publicationHemostasis and Thrombosis
Subtitle of host publicationMethods and Protocols
EditorsEmmanuel J. Favaloro , Robert C. Gosselin
Place of PublicationNew York
Chapter26
Pages405-415
Number of pages11
Edition2nd
ISBN (Electronic)9781071631751
DOIs
Publication statusPublished - 2023

Publication series

NameMethods in Molecular Biology
Volume2663
ISSN (Print)1064-3745
ISSN (Electronic)1940-6029

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