Table 1 Warkentin's 4Ts scoring system
| Â | Score | Â | Â |
|---|---|---|---|
4Ts | 2 points | 1 points | 0 points |
Thrombocytopenia | Platelet count fall >50% or platelet nadir 20 × 109/l | Platelet count fall 30 to 50% or platelet nadir (10 to 19) × 109/l | Platelet count fall <30% or platelet nadir <10 × 109/l |
Timing of platelet count fall | Clear onset between days 5 and 10 or platelet fall <1 day (prior heparin exposure within 30 days) | Consistent with days 5 to 10 fall but not clear (for example, missing platelet counts); onset after day 10; or fall <1 day (prior heparin exposure 30 to 100 days ago) | Platelet count fall <4 days without recent exposure |
Thrombosis or other sequelae | New thrombosis (confirmed); skin necrosis at heparin injection sites; acute systemic reaction post intravenous unfractionated heparin bolus | Progressive or recurrent thrombosis, non-necrotizing (erythematous) skin lesions at heparin injection sites; suspected but unproven thrombosis | None |
Other causes of thrombocytopenia | None apparent | Possible | Definite |