Table 1

Warkentin's 4Ts scoring system

Score

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

Scoring system modified from [23]: 0 to 3, low; 4 to 5, intermediate; 6 to 8, high.

Ricci and Ronco Critical Care 2009 13:227   doi:10.1186/cc7961