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Double-Negative (PF4-Negative/SRA-Negative) Heparin-Induced Thrombocytopenia

Published:October 14, 2022DOI:https://doi.org/10.1016/j.amjmed.2022.09.023
      Heparin-induced thrombocytopenia (HIT) is a disorder characterized by antibody-mediated platelet activation and vascular thrombosis in patients exposed to heparin. Traditionally, the diagnosis is supported by platelet-factor 4 (PF4)/heparin enzyme-immunoassay (EIA) and confirmed with a functional assay, like the serotonin release assay (SRA). We describe a patient with a clinical course highly suspicious for HIT despite an initially weakly positive, then negative, PF4 antibody and repeatedly negative SRA. This should alert clinicians to the growing evidence of double-negative (PF4 negative/SRA negative) HIT as a clinical entity.
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