The HEP score (HIT Expert Probability score) is a clinical prediction tool designed to estimate the pre-test probability of heparin-induced thrombocytopenia (HIT). It was created from the consensus of 26 international HIT experts to address some limitations of the traditional 4T’s score, especially in complex patients and less-experienced clinicians.
HEP Score (HIT Expert Probability)
Pre-test probability model for heparin-induced thrombocytopenia (HIT) based on expert consensus.
HEP score • approx –16 to 19
HEP Score Inputs
Select the single most appropriate option in each section. For “other causes”, select all that apply.
Clinical decision support only.
This calculator does not diagnose HIT and must be interpreted alongside clinical judgement,
laboratory findings and local guidelines.
1. Fall in platelet count from peak to nadir
Relative fall since heparin exposure (from highest to lowest platelet count).
2. Timing of platelet fall vs heparin exposure
Choose the single best description (consider whether there was prior heparin exposure within 100 days).
3. Nadir platelet count
Lowest platelet count observed (× 10⁹/L).
4. Thrombosis
New or progressive venous/arterial thrombosis temporally related to heparin.
5. Skin necrosis at subcutaneous heparin injection sites
6. Acute systemic reaction after IV heparin bolus
Sudden cardiorespiratory or hypotensive reaction temporally associated with IV heparin.
7. Bleeding, petechiae or bruising
Spontaneous bleeding manifestations (tend to argue against HIT).
8. Other causes of thrombocytopenia
Select all that apply. “No other cause identified” will be treated as mutually exclusive with the others.
