Table 2.
HIT expert probability (HEP) score
| Clinical feature | Score |
|---|---|
| 1. Magnitude of fall in platelet count (measured from peak platelet count to nadir platelet count since heparin exposure) | |
| a. < 30% | −1 |
| b. 30%–50% | 1 |
| c. > 50% | 3 |
| 2. Timing of fall in platelet count | |
| For patients in whom typical onset HIT is suspected | |
| a. Fall begins < 4 days after heparin exposure | 0 |
| b. Fall begins 4 days after heparin exposure | 2 |
| c. Fall begins 5–10 days after heparin exposure | 3 |
| d. Fall begins 11–14 days after heparin exposure | 2 |
| e. Fall begins > 14 days after heparin exposure | −1 |
| For patients with previous heparin exposure in last 100 days in whom rapid onset HIT is suspected | |
| f. Fall begins < 48 h after heparin re-exposure | 2 |
| g. Fall begins > 48 h after heparin re-exposure | −1 |
| 3. Nadir platelet count | |
| a. ≤ 20 × 109 L−1 | −2 |
| b. > 20 × 109 L−1 | 2 |
| 4. Thrombosis (Select no more than one) | |
| For patients in whom typical onset HIT is suspected | |
| a. New VTE or ATE ≥ 4 days after heparin exposure | 3 |
| b. Progression of pre-existing VTE or ATE while receiving heparin | 2 |
| For patients in whom rapid onset HIT is suspected | |
| c. New VTE or ATE after heparin exposure | 3 |
| d. Progression of pre-existing VTE or ATE while receiving heparin | 2 |
| 5. Skin necrosis | |
| a. Skin necrosis at subcutaneous heparin injection sites | 3 |
| 6. Acute systemic reaction | |
| a. Acute systemic reaction after intravenous heparin bolus | 2 |
| 7. Bleeding | |
| a. Presence of bleeding, petechiae or extensive bruising | −1 |
| 8. Other causes of thrombocytopenia (Select all that apply) | |
| a. Presence of a chronic thrombocytopenic disorder | −1 |
| b. Newly initiated non-heparin medication known to cause thrombocytopenia | −2 |
| c. Severe infection | −2 |
| d. Severe DIC (defined as fibrinogen < 100 mg dL−1 and D-dimer > 5.0 μg mL−1) | −2 |
| e. Indwelling intra-arterial device (e.g. IABP, VAD, ECMO) | −2 |
| f. Cardiopulmonary bypass within previous 96 h | −1 |
| g. No other apparent cause | 3 |
VTE, venous thromboembolism; ATE, arterial thromboembolism; DIC, disseminated intravascular coagulation; IABP, intra-aortic balloon pump; VAD, ventricular assist device; ECMO, extracorporeal membrane oxygenation.