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Heparin-induced thrombocytopenia

Last reviewed: 30 Oct 2023
Last updated: 20 Jun 2023



History and exam

Key diagnostic factors

  • history of recent heparin exposure
  • history of HIT
  • absence of conditions and medications that cause thrombocytopenia
  • history of recent surgery or trauma
  • features consistent with recent venous or arterial thromboembolic event (e.g., PE, DVT, stroke, MI)
  • necrosis at heparin injection site(s)
More key diagnostic factors

Other diagnostic factors

  • absence of bleeding
  • signs of adrenal hemorrhagic necrosis
  • acute systemic reaction
  • signs of venous limb gangrene
Other diagnostic factors

Risk factors

  • recent heparin exposure (within past 100 days)
  • recent orthopedic or cardiovascular surgery
  • female sex
More risk factors

Diagnostic investigations

1st investigations to order

  • CBC
More 1st investigations to order

Investigations to consider

  • 4Ts score
  • HIT antigen assay
  • HIT functional assay
  • coagulation studies
  • venous Doppler ultrasound
  • computed tomography pulmonary angiogram (CTPA)
  • ventilation-perfusion scan (V/Q scan)
  • cerebral computed tomography venogram
  • magnetic resonance venography (head)
More investigations to consider

Treatment algorithm


suspected HIT with 4Ts score ≥4, or confirmed acute HIT

suspected HIT with 4Ts score ≤3


platelet recovery (subacute HIT A)

remote HIT



Lori-Ann Linkins, MD, MSc(Clin Epi), FRCPC

Associate Professor

Department of Medicine

McMaster University

Thrombosis Consultant

Juravinski Hospital and Cancer Centre





LL is an author of several references cited in this topic.

Peer reviewers

Jeffrey S. Wasser, MD

Assistant Clinical Professor of Medicine

Acting Associate Chair of the Division of Hematology and Medical Oncology

University of Connecticut School of Medicine




JSW declares that he has no competing interests.

Henry Watson, MD, FRCP, FRCPath

Consultant Haematologist

Aberdeen Royal Infirmary

Foresterhill Health Campus




HW declares that he has no competing interests.

Simon Davidson, MPhil

Clinical Scientist

Royal Brompton Hospital

Honorary Clinical Lecturer

Imperial College London




SD is a consultant for Mitsubishi Pharma, the manufacturer of argatroban.

  • Heparin-induced thrombocytopenia images
  • Differentials

    • Postoperative state
    • Thrombotic thrombocytopenic purpura
    • Drug-induced thrombocytopenic purpura
    More Differentials
  • Guidelines

    • Guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia
    • Treatment and prevention of heparin-induced thrombocytopenia
    More Guidelines
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