Clinical features that favor a diagnosis of HIT
| Feature . | Comment . |
|---|---|
| Fall in platelet count ≥ 50% | Platelet count fall is 30%-50% in 10% of cases |
| Fall in platelet count begins 5-14 days after heparin exposure | Platelet count fall may occur immediately after heparin re-exposure in patients with a previous recent exposure (ie, rapid-onset HIT) |
| Nadir platelet count ≥ 20 × 109/L | May be lower in cases associated with DIC |
| Thrombosis | May be venous or arterial |
| Unusual manifestations | Skin necrosis at subcutaneous heparin injection sites; anaphylactoid reactions after intravenous heparin bolus; transient global amnesia |
| Absence of petechiae and significant bleeding | |
| Absence of other causes of thrombocytopenia | Such as infection, drugs other than heparin, CPB |
| Feature . | Comment . |
|---|---|
| Fall in platelet count ≥ 50% | Platelet count fall is 30%-50% in 10% of cases |
| Fall in platelet count begins 5-14 days after heparin exposure | Platelet count fall may occur immediately after heparin re-exposure in patients with a previous recent exposure (ie, rapid-onset HIT) |
| Nadir platelet count ≥ 20 × 109/L | May be lower in cases associated with DIC |
| Thrombosis | May be venous or arterial |
| Unusual manifestations | Skin necrosis at subcutaneous heparin injection sites; anaphylactoid reactions after intravenous heparin bolus; transient global amnesia |
| Absence of petechiae and significant bleeding | |
| Absence of other causes of thrombocytopenia | Such as infection, drugs other than heparin, CPB |