HIT Expert Probability (HEP) Score for Heparin-Induced Thrombocytopenia Clinical Calculator and Pathways

Thrombocytopenia Features

Type of HIT Onset Suspected

Typical Rapid

Magnitude of Platelet Count Fall

Magnitude of Platelet Count Fall

< 30%

-1

30-50

> 50%

Timing of Platelet Count Fall

Fall begins <4 days after heparin exposure

-2

Fall begins 4 days after heparin exposure

Fall begins 5-10 days after heparin exposure

Fall begins 11-14 days after heparin exposure

Fall begins >14 days after heparin exposure

-1

Timing of Platelet Count Fall

Heparin exposure in past 100 days

Fall begins <48 hours after heparin re-exposure

Fall begins >48 hours after heparin re-exposure

-1

Nadir Platelet Count

≤ 20

-2

> 20

Thrombosis

New VTE or ATE ≥4 days after heparin exposure

Progression of pre-existing VTE or ATE while recieivng heparin

Thrombosis

New VTE or ATE after heparin exposure

Progression of pre-existing VTE or ATE while recieivng heparin

Skin Necrosis at Subcutaneous Heparin Injection Sites

Yes

Acute Systemic Reaction After Iv Heparin Bolus

Yes

Presence of Bleeding, Petechiae or Extensive Bruising

Yes

-1

Other Causes of Thrombocytopenia

Presence of Chronic Thrombocytopenic Disorder

Yes

-1

Newly Initiated Non-Heparin Medication Known to Cause Thrombocytopenia

Yes

-2

Severe Infection

Yes

-2

Severe DIC

Fibrinogen <100 mg/dL and D-dimer > 5 µg/mL

Yes

-2

Indwelling Intra-arterial Device

Ex: IABP, VAD, ECMO

Yes

-1

Cardiopulmonary Bypass within Previous 96 Hours

Yes

-1

Source: Cuker A, Arepally G, Crowther MA, Rice L, Datko F, Hook K, Propert KJ, Kuter DJ, Ortel TL, Konkle BA, Cines DB. The HIT Expert Probability (HEP) Score: a novel pre-test probability model for heparin-induced thrombocytopenia based on broad expert opinion. J Thromb Haemost. 2010; 8: 2642–50.

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

Thrombocytopenia Features

Other Causes of Thrombocytopenia

Interpretation