Skip to main content

Table 2 The 4 T's score [32]

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

  1. *First day immunizing heparin exposure considered day zero; the day the platelet count begins to decrease is considered the day of onset of thrombocytopenia.