From: Heparin-induced thrombocytopenia in the ICU: an overview
 | Score | ||
---|---|---|---|
4 T Category | 2 | 1 | 0 |
Thrombocytopenia | Platelet count decrease > 50% or platelet nadir ≥ 20 × 109/L | Platelet count decrease 30-50% or platelet nadir 10-19 × 109/L | Platelet count decrease < 30% or platelet nadir < 10 × 109/L |
Time to platelet count decrease* | Clear onset between days 5-10 or platelet count decrease ≤ 1 day (prior heparin exposure within 100 days) | Consistent with decrease between days 5-10, but not clear (e.g., missing platelet counts); onset after day 10 | Platelet count decrease < 4 days without recent exposure |
Thrombosis or other sequelae | New thrombosis (confirmed); skin necrosis; acute systemic reaction postintravenous heparin | Progressive or recurrent thrombosis; non-necrotizing (erythematous) skin lesions; suspected thrombosis (not proven) | None |
Other causes of thrombocytopenia | None apparent | Possible | Definite |