Wednesday, March 9, 2016

Q: How HIT Expert Probability (HEP) Score differs from 4 T's score in the management of Heparin Induced Thrombocytopenia (HIT)?


Answer: 

In HEP score, points are subtracted or added depending on bleeding or presence of devices or other causes of Thrombocytopenia. It is an excellent measuring score but may be cumbersome. A HEP score cut-off of 2 would lead to 100% sensitivity and 60% specificity while a cut-off of 5 would maximize sensitivity/specificity at 86% and 88%, respectively,


Clinical FeaturePresentationScore
Magnitude of fall in platelet count (measured from peak to nadir since heparin exposure)< 30%-1
30-50%+1
>50%+3
Timing of fall in platelet countFor patients in whom typical onset HIT is suspected:
Fall begins < 4 days after heparin exposure-2
Fall begins 4 days after heparin exposure+2
Fall begins 5-10 days after heparin exposure+3
Fall begins 11-14 days after heparin exposure+2
Fall begins > 14 days after heparin exposure-1
For patients with previous heparin exposure in the last 100 days in whom rapid onset HIT is suspected:
Fall begins < 48 hours after heparin exposure+2
Fall begins > 48 hours after heparin exposure-1
Nadir platelet count≤ 20 × 109 L−1-2
> 20 × 109 L−1+2
Thrombosis
(select no more than one)
For patients in whom typical onset HIT is suspected:
New VTE or ATE > 4 days after heparin exposure+3
Progression of pre-existing VTE/ATE while receiving heparin+2
For patients in whom rapid onset HIT is suspected:
New VTE or ATE after heparin exposure+3
Progression of pre-existing VTE /ATE while receiving heparin+2
Skin necrosisSkin necrosis at subcutaneous heparin injection sites+3
Acute systemic reactionAcute systemic reaction after intravenous heparin bolus+2
BleedingPresence of bleeding, petechiae, or extensive bruising-1
Other causes of thrombocytopenia (select all that apply)Presence of a chronic thrombocytopenic disorder-1
Newly initiation non-heparin med known to cause thrombocytopenia-2
Severe infection-2
Severe DIC (fibrinogen < 100 mg/dL and D-dimer > 5 mcg/ml)-2
Indwelling intra-arterial device (IABP, VAD, ECMO)-2
Cardiopulmonary bypass within previous 96 hrs-1
No other apparent cause+3
VTE=venous thromboembolism; ATE=arterial thromboembolism; DIC=disseminated intravascular coagulation



References: 

1. Cuker A, Arepally G, Crowther MA, 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. 

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

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