What is the clinical manifestation of heparin-induced thrombocytopenia (HIT)?

Updated: Sep 18, 2020
  • Author: Daniel R Ouellette, MD, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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HIT may manifest clinically as extension of the thrombus or formation of new arterial thrombosis. HIT should be suspected whenever the patient's platelet count falls to less than 100,000/µL or less than 50% of the baseline value, generally after 5-15 days of heparin therapy. For patients receiving heparin where the risk of HIT is thought to be greater than 1%, guidelines suggest that platelet counts be obtained every two or three days from day 4 to day 14 of therapy, or until the heparin is stopped (grade 2C). [5] The definitive diagnosis is made by performing a platelet activation factor assay.

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