4Ts Score for Heparin-Induced Thrombocytopenia
Differentiates patients with HIT from those with other causes of thrombocytopenia.
When to Use
Pearls/Pitfalls
Why Use
Platelet count fall >50% AND platelet nadir ≥20
+2Platelet count fall 30–50% OR platelet nadir 10–19
+1Platelet count fall <30% OR platelet nadir <10
0Clear onset between days 5–10 OR platelet fall ≤1 day (prior heparin exposure within 30 days)
+2Consistent with days 5–10 fall, but not clear; onset after day 10 OR fall ≤1 day (prior heparin exposure 30–100 days ago)
+1Platelet count fall <4 days without recent exposure
0New thrombosis OR skin necrosis; acute systemic reaction post-IV heparin bolus
+2Progressive OR recurrent thrombosis; non-necrotizing skin lesions; suspected thrombosis (not proven)
+1None
0None apparent
+2Possible
+1Definite
0Result:
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