Hematology
4Ts Clinical Probability Score for Heparin-Induced Thrombocytopenia (HIT)
Calculates the 4Ts score (0–8) to evaluate pre-test probability of HIT and guide immediate non-heparin anticoagulation.
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Parameters
4Ts Clinical Probability Score for Heparin-Induced Thrombocytopenia (HIT) Result
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Formula
4Ts Score = Thrombocytopenia (0–2) + Timing (0–2) + Thrombosis (0–2) + oTher causes (0–2)
Score 0–3: Low (<5%) | 4–5: Intermediate (~14%) | 6–8: High (~64%)Clinical Pearls
The universally recommended clinical decision score for assessing HIT pre-test probability, preventing both catastrophic thrombosis and unwarranted heparin cessation.
Limitations
The 4Ts score can have reduced specificity in post-cardiac surgery ICU patients due to baseline cardiopulmonary bypass-induced platelet drops.