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

HEP Score (HIT Expert Probability)

Estimates the pre-test probability of heparin-induced thrombocytopenia (HIT) from the platelet fall, thrombosis, and competing causes using the expert-consensus HEP model; it does not diagnose or exclude HIT — confirm with anti-PF4/heparin and functional assays.

Magnitude of fall in platelet count (peak to nadir since heparin)

Timing of platelet fall relative to heparin exposure (single mutually-exclusive branch)

Nadir platelet count

Thrombosis

Skin necrosis at subcutaneous heparin injection sites

Acute systemic reaction after IV heparin bolus

Bleeding, petechiae, or extensive bruising present

Other cause: chronic thrombocytopenic disorder present

Other cause: newly initiated non-heparin medication that can cause thrombocytopenia

Other cause: severe infection

Other cause: severe (overt) DIC — fibrinogen <100 mg/dL AND D-dimer >5.0 ug/mL (answer No if only one criterion is met)

Other cause: indwelling intra-arterial device (e.g., IABP, VA-ECMO cannula)

Other cause: cardiopulmonary bypass within the prior 96 hours