Proto
MD
← Back to ProtoMD
Clinical Calculator
Hematology V1.0
4Ts
Score
Pre-Test Probability of Heparin-Induced Thrombocytopenia
Primary Reference
Lo GK, et al.
J Thromb Haemost 2006; 4:759–765
Clinical Assessment
1. Thrombocytopenia
Fall <30% or nadir <10K (0)
Fall 30–50% or nadir 10–19K (+1)
Fall >50% AND nadir ≥20K (+2)
2. Timing of Platelet Fall
<4 days, no recent heparin (0)
Consistent with d5–10 but unclear (+1)
Clear d5–10 or ≤1d with recent heparin (+2)
3. Thrombosis
None (0)
Progressive/recurrent/suspected (+1)
New confirmed thrombosis/skin necrosis (+2)
4. Other Causes
Definite other cause (0)
Possible other cause (+1)
No other cause apparent (+2)
Calculate 4Ts
Analysis Required
Enter patient parameters to calculate
HIT probability.
—
Points
HIT Probability
—
—
Pre-Test Probability
—
Action
—
Low 0–3
Intermediate 4–5
High 6–8
Breakdown
Clinical Implication
—
References & Original Research
↕ Hover to expand
1
Lo GK, et al.
Evaluation of 4Ts score for HIT diagnosis.
J Thromb Haemost 2006;4:759–765.
View ↗
2
Cuker A, et al.
ASH 2018 guidelines: HIT.
Blood Adv 2018;2:3360–3392.
View ↗