MDCalc

HIT Expert Probability (HEP) Score for Heparin-Induced Thrombocytopenia

Pre-test clinical scoring model for HIT based on broad expert opinion.

Thrombocytopenia Features

Type of heparin-induced thrombocytopenia (HIT) onset suspected

Magnitude of platelet count fall

Peak to nadir count since heparin

Nadir platelet count

Skin necrosis at subcutaneous heparin injection sites
Acute systemic reaction after IV heparin bolus
Presence of bleeding, petechiae or extensive bruising

Other Causes of Thrombocytopenia

Presence of chronic thrombocytopenic disorder
Newly initiated non-heparin medication known to cause thrombocytopenia
Severe infection
Severe disseminated intravascular coagulation (DIC)
Fibrinogen <100 mg/dL and D-dimer >5 µg/mL
Indwelling intra-arterial device
IABP, VAD, ECMO
Cardiopulmonary bypass within previous 96 hours
No other apparent cause

Result:

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Critical Actions
  • Consider using the 4Ts scoring system in conjunction with the HEP score as an alternative evaluation tool prior to time-consuming antibody testing for HIT or empiric substitution of heparin for another anti-coagulant.
  • Consider further laboratory evaluation for HIT or switching to a non-heparin derived anti-coagulant in those patients that are above the screening threshold for HIT based on their HEP score.
  • Larger studies of the HEP score are likely necessary prior to broader independent implementation.
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