4Ts Score For Heparin-Induced Thrombocytopenia

Thrombocytopenia

Platelet count fall >50% AND platelet nadir ≥20

Platelet count fall 30–50% OR platelet nadir 10–19

Platelet count fall <30% OR platelet nadir <10

Timing of platelet count fall

Clear onset between days 5–10 OR platelet fall ≤1 day Prior heparin exposure within 30 days

Consistent with days 5–10 fall, but not clear; onset after day 10 OR fall ≤1 day prior heparin exposure 30–100 days ago

Platelet count fall <4 days without recent exposure:

Thrombosis or other sequelae

Progressive OR recurrent thrombosis; non-necrotizing skin lesions; suspected thrombosis Not proven

None

New thrombosis OR skin necrosis; acute systemic reaction post-IV heparin bolus:

Other causes for thrombocytopenia

None apparent:

Possible:

Definite:

Result
Note! This is not a diagnosis. The calculations that are provided are estimates based on averages.
4Ts Score