HIT Expert Probability [HEP] Score

NOTE: Whilst we have done our utmost to ensure the accuracy of the data in this section, users should access the original publications. This will also allow you to see how the algorithm was created, the population studied and any limitations to the study.

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1. Cuker A, Arepally G, et al. 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.

2. Joseph L, Gomes MP, et al. External validation of the HIT Expert Probability (HEP) score. Thromb Haemost. 2015; 113: 633-40.

Fall in Platelet Count from Peak Platelet Count to the Nadir Platelet Count since Heparin Exposure
	<30%	-1 Point
	30% - 50%	1 Point
	>50%	3 Points
Timing of the Fall in Platelet Count
i. For patients in whom typical onset HIT is suspected
	Fall in platelet count occurs <4 days after exposure to heparin	-2 Points
	Fall in platelet count occurs 4 days after exposure to heparin	2 Points
	Fall in platelet count occurs 5-10 days after exposure to heparin	3 Points
	Fall in platelet count occurs 11-14 days after exposure to heparin	2 Points
	Fall in platelet count occurs >14 days after exposure to heparin	-1 Point
ii. For patients with previous Heparin exposure within 100 days and in whom rapid onset HIT is suspected
	Fall in platelet count occurs <48 hrs after exposure to heparin	2 Points
	Fall in platelet count occurs >48 hrs after exposure to heparin	-1 Point
Nadir Platelet Count
	≤ 20 x 10⁹/L	-2 Points
	>20 x 10⁹/L	2 Points
Thrombosis
i. For patients in whom typical onset HIT is suspected
	New venous or arterial thrombosis ≥4 days after heparin exposure	3 Points
	Progression of venous or arterial thrombosis whilst receiving heparin	2 Points
ii. For patients with previous Heparin exposure within 100 days and in whom rapid onset HIT is suspected
	New venous or arterial thrombosis ≥4 days after heparin exposure	3 Points
	Progression of venous or arterial thrombosis whilst receiving heparin	2 Points
Skin necrosis at subcutaneous Heparin Injections site[s]
	Yes	3 Points
	No	0 Points
Acute Systemic Reaction after iv Heparin infusion
	Yes	2 Points
	No	0 Points
Bleeding [Bleeding/petechiae or bruising]
	Yes	-1 Point
	No	0 Points
Other causes of Thrombocytopaenia not evident [Select all that apply]
	Presence of a chronic thrombocytopenic disorder	-1 Point
	Newly commenced treatment [non-heparin] known to cause thrombocytopaenia]	-2 Points
	Severe infection	-2 Points
	DIC [Fibrinogen <1g/L & D-dimer >5.0µg/mL	-2 Points
	Indwelling arterial device	-2 Points
	Cardiopulmonary bypass within 96hr	-1 Point
	No other cause identified	3 Points

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HEP Score¹
2	With a cut-off HEP score of 2, the HEP score was.. Sensitivity: 100% Specificity: 60% ..for a diagnosis of Heparin Induced Thrombocytopaenia [HIT]
5	With a cut-off HEP score of 5, the HEP score was.. Sensitivity: 86% Specificity: 88% ..for a diagnosis of Heparin Induced Thrombocytopaenia [HIT]